GENITOURINARY IMAGING 2 Flashcards
KIDNEY ANATOMY
Does US over or under estimate renal length?
Ultrasound (US) often underestimates the true renal length because of technical difficulties in imaging the entire kidney.
19F Hypertensive
kypokalaemia
elevated aldosterone
Juxtaglomerular Tumor (Reninoma)
- Secretion of renin causes HTN, hypernatremia, and hypokalemia (secondary aldosteronism).
- Most patients undergo angiography as part of the workup for HTN.
- Tumors appear as small hypovascular masses. Rare.
Reninoma is a tumour of the cells of the juxtaglomerular apparatus that produces excessive amounts of renin, resulting in a secondary form of hyperaldosteronism, manifesting clinically with hypertension (HT) and hypokalaemia1. This renal tumour is predominant in females, with a peak incidence between the second and third decade of life and, although uncommon, it is a treatable cause of HT2. It should be suspected in any patient with refractory HT associated with hypokalaemia and high levels of aldosterone.
We present the first case of reninoma reported in Argentina in a young woman with refractory HT and hypokalaemia.
In 1967, Robertson et al.6 reported the first renin-producing tumour. Kihara et al. later called them “juxtaglomerular cell tumours”7. These tumours are very uncommon, with their incidence peaking between the second and third decade of life and they are predominantly found in females, originating in the myoendocrine cells of the renal juxtaglomerular apparatus, although the production of renin by different tumours has also been demonstrated, such as Wilms tumours, carcinoid tumours, renal oncocytoma and renal cell carcinoma8,9. In accordance with the presence or absence of symptoms, JCT may occur as: a “typical” variant in the majority of cases and manifests with HT, hypokalaemia, high plasma renin and secondary hyperaldosteronism; an “atypical” variant, in which HT is not accompanied by hypokalaemia; and a third “non-functioning” variant, which occurs without HT and with normal levels of potassium10,11.
Plasma renin activity (PRA) and plasma aldosterone (PA)
https://www.revistanefrologia.com/en-juxtaglomerular-cell-tumour-as-curable-articulo-X2013251415054971
SIGN
What sign is this and what does it indicate?
Case Discussion
Left sided duplicated collecting system with the upper moiety obstruction, and non-functioning. It displaces the lower pole moiety inferiorly, mimicking the appearance of a drooping lily.
The drooping lily sign refers to the inferolateral displacement of the opacified lower pole moiety due to an obstructed (and unopacified) upper pole moiety in duplicated collecting system.
Case courtesy of Dr Mohammad Taghi Niknejad, Radiopaedia.org, rID: 54354
What are the 6 radiographic features of uretal duplication?
What sign is this?
Radiographic Features (Lebowitz) ( Fig. 11.39 )
- Increased distance from top of nephrogram to collecting system: hydronephrotic upper pole moiety causes mass effect (1)
- Abnormal axis of collecting system (2)
- Concave upper border of renal pelvis (3)
- Diminished number of calyces compared with normal side; drooping lily sign (4)
- Lateral displacement of kidney and ureter (5)
- Spiral course of ureter (6)
- Filling defect in the bladder (ureterocele)
Case courtesy of Dr Mohammad Taghi Niknejad, Radiopaedia.org, rID: 54354
What is a renal Adenoma?
Adenoma
Best described as adenocarcinoma with no metastatic potential. Usually detected at autopsy.
Peripelvic Cyst
- Originates from sinus structures, most likely lymphatic in origin
- May be indistinguishable from hydronephrosis on US, requiring an IVP or CT for definitive diagnosis
- Attenuated, stretched infundibula
- IVP differential diagnosis (DDx): renal sinus lipomatosis
PATHOLOGICAL SPECIMEN
- What is the inheritance pattern?
- What is the incidence?
- What are the clinical findings?
- What is the treatment?
- What is the malignancy risk?
Adult Polycystic Kidney Disease (Apkd) ( Fig. 4.5 )
- Intro:
- Cystic dilatation of collecting tubules, as well as nephrons
- (unlike MCD and infantile polycystic kidney disease in which only the collecting tubules are involved).
- AD trait (childhood type is AR).
- Incidence:
- 0.1% (most common form of cystic kidney disease; accounts for 10% of patients on chronic dialysis).
- Clinical
- Slowly progressive renal failure.
- Symptoms usually begin in 3rd or 4th decade, but clinical onset is extremely variable, ranging from palpable cystic kidneys at birth to multiple cysts without symptoms in old age.
- Enlarged kidneys may be palpable.
- Treatment
- Treatment is with dialysis and transplant.
- Malignancy
- No increased risk of malignancy.
What are the complications of RF Ablation (re RCC)?
Complications
- Pain may last for several days to weeks.
- Postablation syndrome:
- fever, malaise, and body aches.
- Severity is related to volume of tissue ablated.
- Hemorrhage, often self-limited
- Injury to ureter, central collecting system, or adjacent organs
What are the 6 associations of this condition?
Horseshoe Kidney
- Associations
- UPJ obstruction, 30%
- Ureteral duplication, 10%
- Genital anomalies
- Other anomalies: anorectal, cardiovascular, musculoskeletal anomalies
Case courtesy of Dr Aditya Shetty, Radiopaedia.org. From the case rID: 27958
What is the staging for this condition?
Renal pelvis TCC
Staging
- Stage I: mucosal lamina propria involved
- Stage II: into, but not beyond, muscular layer
- Stage III: invasion of adjacent fat/renal parenchyma
- Stage IV: metastases
Medullary Cystic Disease
What is the cause of this disease?
Medullary Cystic Disease (MCD) ( Fig. 4.4 )
Spectrum of diseases characterized by tubulointerstitial fibrosis.
Patients usually present with azotemia and anemia and subsequently progress to end-stage failure.
Azotemia: Elevated levels of urea and other nitrogen compounds in the blood.
SYNDROMES
What syndromes/diseases are a/w renal Cysts?
What are the differences in the morphology of the cysts?
- TS
- VHL
- BHD
- ARPCKD
- ADRCKD
- DICER
- Nephronopthisis
- Asphyxiating thoracic dys- trophy (Jeune syndrome)
- Meckel-Gruber syndrome;
- Joubert syndrome and related disorders;
- Ellis–van Creveld syndrome;
- short rib–polydactyly group
Fig. 63.1 (A) Postcontrast CT image shows bilateral renal cysts. There is a large cyst within the right kidney with thick enhancing septations (arrowhead). Note the multiple pancreatic cysts (arrow). (B) Axial image shows a mixed solid and cystic lesion in the left kidney (arrowhead), along with an enhancing nodule in the chord (arrow). (C)An additional complex cyst with enhancing septation is seen in the right kidney (arrowhead), along with a small enhancing lesion in the left kidney (arrowhead).
SYNDROMES
Re ADPCKD describe the following:
Type of inheritance?
Genes?
Renal findings?
Associated findings?
AD
PKD1, PKD2
(ciliopathy)
Multiple bilateral variably sized renal cortical and medul-
lary cysts; number and size
of cysts increase with time; nephrolithiasis; chronic kidney disease typically occurs in late adulthood
Ductal plate malformations (eg, congenital hepatic fibrosis); extrarenal cysts (eg, liver, pancreas, seminal vesicles); intracranial aneu- rysms (typically in adult- hood)
Describe the staging system of RCC
Staging
- Stage I:
- tumor confined to kidney
- Stage II:
- extrarenal (may involve adrenal gland) but confined to Gerota fascia
- Stage III:
- A: venous invasion (renal vein);
- B: lymph node metastases;
- C: both
- Stage IV:
- A: direct extension into adjacent organs through Gerota fascia;
- B: metastases
- Lungs, 55%
- Liver, 25%
- Bone, 20% (classic lesions are lytic, expansile)
- Adrenal, 20%
- Contralateral kidney, 10%
- Other organs, <5%
Complicated Cysts
- Complicated cysts are cysts that do not meet the criteria of simple cysts and thus require further workup.
- Case Discussion
- This is a classic example of a Bosniak type IV cyst - with an abnormal cyst first identified on ultrasound proceeding to three phase CT imaging.
- It is made more difficult by the bilateral cystic renal disease, but the left mid/upper pole cyst contained a significant solid element.
- The patient is due for a total nephrectomy - the histopathological outcome will be added when available.
Case courtesy of Dr Ian Bickle, Radiopaedia.org, rID: 24244
KIDNEY ANATOMY
L and R kidneys should be within x cm of eachother?
Left and right kidney size should not vary more than 1cm.
What is the prognosis of RCC?
5 yr survival
Stage 1, 2, 3, 4?
What are the unual behaviours of RCC?
Prognosis
5-year survival:
- stage I = 81%
- stage II = 74%
- stage III = 53%
- stage IV = 8%
- Tumors often have atypical behavior:
- Late recurrence of metastases:
- 10% recur 10 years after nephrectomy.
- Some patients survive for years with untreated tumor.
- Spontaneous regression of tumor has been reported but is very rare.
- Late recurrence of metastases:
Dromedary hump: parenchymal prominence in left kidney; results from compression of adjacent spleen
Case courtesy of Assoc Prof Craig Hacking, Radiopaedia.org, rID: 53697
Angiomyolipoma (Aml)
- Hamartomas containing fat, smooth muscle, and blood vessels.
- Small lesions are not treated; large and symptomatic lesions are resected or embolized.
- Unlikely to bleed if <4 cm.
- Complication: tumors may spontaneously bleed because of their vascular elements.
Case courtesy of Dr Behrang Amini, Radiopaedia.org, rID: 35925
Axial CT through the kidneys shows a fat-attenuation lesion in the left kidney with a perirenal collection, most likely blood. This is consistent with a bleeding angiomyolipoma.
What are the 4 types of this condition?
Medullary cystic disease
Types
- Familial nephronophthisis, 70%, autosomal recessive (AR)
- Juvenile type, onset at age 3–5 years (most common)
- Adult MCD, 15%, autosomal dominant (AD)
- Renal-retinal dysplasia, 15%; recessive associated with retinitis pigmentosa
Radiopedia
- Medullary cystic disease complex belongs to group of paediatric cystic renal diseases characterised by progressive tubular atrophy with glomerulosclerosis (chronic tubulointerstitial nephritis) and multiple small medullary cysts.
- Epidemiology
- There is no recognised gender predilection
- Clinical presentation
- Presentation with polydipsia and polyuria, due to initial tubular injury, tends to progress to end stage renal failure, growth retardation, lethargy.
- Three clinical variants based on age of onset for end stage renal disease (ESRD):
- infantile: before 2 years of age
- juvenile (a.k.a. nephronophthisis): most common form, age of onset 10
- adolescent (a.k.a. medullary cystic kidney disease): usually develops in patients in their thirties
- There can be a clinical triad comprising of uraemia, anaemia, and salt wasting (hyponatraemia, hypokalaemia).
- Pathology
- It comprises a group of related conditions characterised by multiple cysts typically at the corticomedullary junction and medulla. The medullary cysts are small. There can be associated atrophy and fibrosis of the basement membrane of the proximal and distal tubules which leads into interstitial fibrosis and end stage renal disease.
- Variants
- familial nephronophthisis:
- autosomal recessive (40%)
- sporadic: non-familial (20%)
- retinal renal syndrome:
- autosomal recessive (15%) associated with retinitis pigmentosa
- adult onset medullary cystic disease:
- autosomal dominant (15%)
- familial nephronophthisis:
- Radiographic features
- Normal to small kidneys with multiple small (<1.5 cm) medullary cysts (sometimes cysts are too small to visualise) at the corticomedullary junction.
What is RF Ablation
Re RCC?
What are the 5 indications?
Radiofrequency Ablation of RCC
- Radiofrequency, cryoablation, and microwave ablation are noninvasive options for treating RCC.
- High-frequency alternating current is applied to a metallic applicator placed within the tumor.
- The surface area of the electrode is small, which results in a high current density at the electrode surface resulting in heat.
- When tissues reach temperatures greater than 50°C, they undergo necrosis.
Indications
- Comorbidities and contraindications to conventional or laparoscopic surgery
- Refusal of conventional surgery
- Compromised renal function
- Patients who have undergone a nephrectomy
- High risk of recurrence (e.g., VHL disease)
What are the imaging features of AML?
Imaging Features
- Fat appears hypodense (CT), hyperechoic (US), and hyperintense (T1W).
- The presence of fat in a renal lesion is virtually diagnostic of AML. There have been only a few case reports of fat in RCC or in oncocytomas.
- Five percent do not demonstrate fat on CT.
- Caveat: be certain that fat associated with a large mass is not trapped in renal sinus or peripheral fat.
- Predominance of blood vessels
- Strong contrast enhancement
- T2W hyperintensity
- Predominance of muscle:
- signal intensity (SI) similar to that of RCC
- AMLs do not contain calcifications;
- if a lesion does contain calcification, consider other diagnosis, such as RCC.
- Angiography:
- tortuous, irregular, aneurysmally dilated vessels are seen in 3%.
- Presence depends on the amount of angiomatous tissue.
- Predominantly myxomatous AMLs may be hypovascular.
Case Discussion
- Predominantly echogenic lesion involving the upper pole of the right kidney associated with more complex appearing perinephric collection.
- CT scan of the abdomen confirms the presence of a fatty lesion in the upper pole of the right kidney consistent with angiomyolipoma complicated by haemorrhage.
- Incidental two tiny hepatic haemangiomas.
- Perirenal haemorrhage without a history of trauma complicating an angiomyolipoma is known as Wunderlich syndrome.
- If perirenal haemorrhage is encountered on ultrasound, a thorough workup should be performed to exclude a bleeding renal cell carcinoma.
- Case courtesy of Dr Hani Makky Al Salam, Radiopaedia.org, rID: 10090
what is this condition
who does it happen to?
- Cystic nephromas, previously known as multilocular cystic nephromas, are rare benign renal neoplasms classically occurring in adult females in the 4th and 5th decades.
- As of the 2016 WHO classification, they are considered distinct from paediatric cystic nephromas which have associated DICER1 gene mutation 10,11,14.
- All different disorders:
- cystic nephroma (adult)
- paediatric cystic nephroma (paediatric)
- cystic partially differentiated nephroblastoma (paediatric)
- As of 2016, the WHO classifies cystic nephroma within the mixed epithelial and stromal tumour (MEST) family along a spectrum of disease 10,13,14. The remainder of this article will discuss the adult form of cystic nephroma.
-
Epidemiology
- overall rare
- adult (typically in the 5th - 6th decades)
- females are predominantly affected
Case courtesy of Dr Roberto Schubert, Radiopaedia.org, rID: 17489
What are are the risk factors for RCC?
What is a/w bilateral tumours?
Risk Factors
- Tobacco use
- Long-term phenacetin use
- VHL disease (bilateral tumors)
- Chronic dialysis (>3 years)
- Family history
What is the management of this lesion?
Oncocytoma
These tumors arise from oncocytes (epithelial cell) of the proximal tubule. Although the majority of lesions are well differentiated and benign, these tumors are usually resected because of their malignant potential and the difficulty in differentiating them from RCC preoperatively.
Can consider performing biopsy followed by observation in poor surgical candidates.
Represent 5% of renal tumors.
Case courtesy of Dr Paul Simkin, Radiopaedia.org, rID: 32824
Milk of Calcium Cyst
- Not a true cyst but a calyceal diverticulum, which may be communicating or closed off
- Contains layering calcific granules (calcium carbonate)
- No pathologic consequence
- Case courtesy of Dr Mohammad Taghi Niknejad, Radiopaedia.org, rID: 62623
- Case Discussion
- A 17mm non-enhancing cyst like lesion is noted adjacent to middle calyces of left kidney; accompanied with dependent hyperdense material.
- Features on CT scan are compatible with left renal milk of calcium cyst. Considered an incidental benign finding that does not require further treatment unless symptomatic.
-
Radiopaedia
- Renal milk of calcium cysts refer to the appearance of a calcium precipitate found either within a calyceal diverticulum, that has lost communication with the collecting system, or within a simple renal cyst.
- Clinical presentation
- Renal milk of calcium cysts are typically asymptomatic.
- Radiographic features
- Plain radiograph
- on erect or decubitus films, renal milk of calcium cysts have a characteristic crescentic opacity with a sharp upper border
- will change shape to a more oval-shaped opacity on supine projections
- Ultrasound
- dependent echogenic material within a hypoechoic cyst that demonstrates reverberation artifact
- posterior shadowing is present when large volumes of milk of calcium are present
- more common in the upper pole of the kidneys
- Plain radiograph
- Treatment and prognosis
- Considered an incidental benign finding that does not require further treatment unless symptomatic.
- Differential diagnosis
- On supine plain radiographs, a renal milk of calcium cyst may be mistaken for a renal calculus.
- Milk of calcium can also occur within the gallbladder.
What are the clincal findings of RCC?
- Hematuria, 50%
- Flank pain, 40%
- Palpable mass, 35%
- Weight loss, 25%
Perinephric Cyst
- Located beneath the renal capsule
- Not true cysts; represent extravasated urine trapped beneath renal capsule (pseudocysts, uriniferous cysts, urinoma)
- CT scan of abdomen shows multiple perinephric cystic fluid collections compressing both the kidneys.
- https://www.researchgate.net/figure/CT-scan-of-abdomen-shows-multiple-perinephric-cystic-fluid-collections-compressing-both_fig2_275123460
What are the imaging features of Medullary Cystic Disease?
Imaging Features
- Small kidneys (as opposed to large kidneys in polycystic disease)
- Multiple small (<2 cm) cysts in medulla
- Cysts may be too small to resolve by imaging, but their multiplicity will result in increased medullary echogenicity and apparent widening of central sinus echoes.
- Cortex is thin and does not contain cysts.
- No Calcifications
KIDNEY ANATOMY
How long and wide are the kidneys usually?
Do IVPs over or under estimate renal length?
Orientation and Size of Kidneys
Kidneys are 3 to 4 lumbar vertebral bodies in length, 12–14 cm long and 5–7 cm wide.
Intravenous pyelograms (IVPs) overestimate the true renal length because of magnification and renal engorgement from osmotic diuresis.
List the 19 different types of renal tumours
4 categories
6,3,8,2
- Renal parenchymal tumors
- Renal cell adenocarcinoma, 80%
- Wilms tumor, 5%
- Adenoma (thought to represent early RCC)
- Oncocytoma
- Nephroblastomatosis
- Mesoblastic nephroma
- Mesenchymal tumors
- Angiomyolipoma (AML)
- Malignant fibrous histiocytoma (MFH)
- Hemangioma
- Other rare tumors
- Renal pelvis tumors
- Transitional cell carcinoma (TCC) <10%
- Squamous cell carcinoma
- Undifferentiated adenocarcinoma tumors
- Benign tumors:
- papilloma
- angioma,
- fibroma
- myoma
- polyp
- Secondary tumors
- Metastases
- Lymphoma
What are the imaging findings of RCC?
What are the contrast enhancement characteristics?
Calcs?
Cystic?
Filling defects?
Size?
What is angiography useful for?
Imaging findings
- Mass lesion: renal contour abnormality, calyceal displacement
- Large variability in signal characteristics on noncontrast CT and MRI depending on the degree of hemorrhage and necrosis
- Contrast enhancement is usually heterogeneous; strong contrast enhancement (>15 HU)
- Calcification, 10%
- Cystic areas (2%–5% are predominantly cystic)
- Filling defects (clots, tumor thrombus) in collecting system and renal veins.
- US appearance
- Hyperechoic: 70% of tumors >3 cm, 30% of tumors <3 cm
- Hypoechoic
- Angiography
- 95% of tumors are hypervascular.
- Caliber irregularities of tumor vessels are typical (encasement).
- Prominent AV shunting, venous lakes
- Angiography may be useful for detection in complicated and equivocal cases:
- Small tumors
- Underlying abnormal renal parenchyma
- VHL disease
- Preoperative embolization
What are the typical imaging features of Oncocytomas?
Imaging Features
- Central stellate scar (CT) and spoke wheel appearance (angiography) are typical but not specific (also seen in adenocarcinoma).
- Well-defined, sharp borders
- Radiographically impossible to differentiate from RCC
- Case Discussion
- A nephrectomy was undertaken for this large renal mass.
- It was a renal oncocytoma on the surgical pathology specimen.
- This typically has a central stellate scar, however the appearances are very similar to the central necrosis observed in many renal cell carcinomas.
- Case courtesy of Dr Ian Bickle, Radiopaedia.org, rID: 78952
What is the incidence of renal involvement in lymphoma?
Which type of lymphoma is more common?
Lymphoma Incidence of renal involvement in lymphoma is 5%
non-Hodgkin lymphoma [NHL] > Hodgkin disease at diagnosis and 30% at autopsy.
What are the imaging features of this condition?
Horseshoe Kidney
- The two kidneys are connected across the midline by an isthmus.
- This is the most common fusion anomaly (other fusion anomalies: cross-fused ectopia, pancake kidney).
- The isthmus may contain parenchymal tissue with its own blood supply or consist of fibrous tissue.
-
Imaging Features
- Abnormal axis of each kidney with lower calyx more medial than upper calyx
- Bilateral malrotation of renal pelvises in anterior position
- Isthmus lies anterior to aorta and inferior vena cava (IVC) but behind inferior mesenteric artery (IMA)
Case courtesy of Dr Aditya Shetty, Radiopaedia.org. From the case rID: 27958
CT PROTOCOL
what is the Stone Protocol
Stone Protocol
- Noncontrast CT of the abdomen and pelvis using 5 mm slice thickness
- Coronal and sagittal reconstructions with 3 mm slice thickness
CT KUB
Last revised by Dr Vikas Shah◉ on 06 Jul 2021
- Computed tomography of kidneys, ureters and bladder (CT KUB) is a quick non-invasive technique for diagnosis of urolithiasis. It is usually considered the initial imaging modality for suspected urolithiasis in an emergency setting 1.
- Indications
- suspected urolithiasis
- haematuria (typically in conjunction with a CT-IVU)
- flank pain
- Purpose
- The purpose of CT KUB is primarily to assess for the presence of urolithiasis. Location of the stone, size, and secondary signs of renal tract obstruction can then be used to gauge the likelihood of passage and guide further management 3.
Case courtesy of Dr Ian Bickle, Radiopaedia.org, rID: 84479
PROCEEDURE
What are the inidcations of Percutaneous Nephrostomy?
What are the steps?
Percutaneous Nephrostomy (Pcn)
- Refers to percutaneous drainage of renal collecting system by catheter placement. Complications: 2%–4% (extravasation of contrast, bleeding)
- Indications
- Hydronephrosis (acute, subacute obstruction)
- Pyonephrosis
Technique ( Fig. 4.2 )
- Preprocedure workup: Check coagulation status.
Cefazolin 2 g IV < 120 kg; 3 g IV > 120 kg and gentamicin 120 mg IV × 1
Penicillin-allergic patients: vancomycin as above and aztreonam 2 g IV
Review all radiographs and determine on plain film where kidneys are located, especially in relation to colon, spleen, and pleural reflections.
- Local lidocaine. Under US guidance, place a 20-gauge introducer system into a posterior, lower pole calyx.
- The inner needle stylet can be removed and free flow of urine checked. Aspirate a small amount for cultures and to mildly decompress the system when urine is obtained.
- Attach connector tubing and inject a small amount of contrast to confirm positioning at the tip of a calyx. Detach the connector tubing carefully to ensure that the needle stays in place.
- Use the microwire to gain access to the renal pelvis. Remove the introducer needle, and insert the plastic sheath that comes with the set.
- Place a 0.038 Amplatz wire through the sheath into the renal collecting system and down the ureter. Depending on the anatomy/obstruction, it may be necessary to use different wire combinations.
- Dilate skin up to 12 Fr.
- Pass 8–10-Fr percutaneous nephrostomy (PCN) catheter over guidewire. Remove stiffener and guidewire. Coil pigtail. Inject contrast to check position of catheter within the renal pelvis. Cut thread.
- In the setting of infection, complete evaluation of the ureter via an antegrade injection is best deferred to a second visit.
PATHOLOGY SPECIMEN
What are the associated findings of this condition?
Associated Findings
- Hepatic cysts, 70%
- Intracranial berry aneurysm, 20%
- Cysts in pancreas and spleen, <5%
What is the paraneoplastic syndrome a/w RCC and the associated hormones?
Paraneoplastic syndrome:
- HTN (renin),
- erythrocytosis (erythropoietin),
- hypercalcemia (PTH),
- gynecomastia (gonadotropin),
- Cushing syndrome (ACTH)
What are the imaging features of Renal Lymphoma?
Imaging Features
- Multiple lymphomatous masses (hypoechoic, hypodense), 50%
- Diffuse involvement of one or both kidneys
- Adenopathy
Case courtesy of Dr Abdallah Al Khateeb, Radiopaedia.org, rID: 47824
What is the finding?
Left Bifid Renal Pelvis
- One pelvis drains upper pole calyces;
- the other drains the middle and lower pole calyces.
- The two pelvises join proximally to the ureteropelvic junction (UPJ).
- Incidence: 10% of population.
- No complications.
Case courtesy of Assoc Prof Craig Hacking, Radiopaedia.org, rID: 55987
Re RCC, what is the classic appearance of bone mets?
Bone, 20% (classic lesions are lytic, expansile)
Bone Metastases
Bone metastases appear in 30% of all patients with disseminated RCC (23). Most bone metastases are associated with severe comorbidity, causing pain and pathologic fractures with subsequent functional impairment. Recent studies have reported that these patients have a high incidence of spinal cord and nerve root compression (27).
On CT images, bone metastases appear as large expansile lytic lesions, most commonly located in the axial skeleton; usually the vertebral bodies are involved more often than the pedicles. Lytic lesions are usually extremely destructive and may be associated with an enhancing soft-tissue component (Fig 4) (13).
What are the complications of this condition?
What is the incidence of this condition?
Ureteral Duplication ( Fig. 11.38 )
- Two ureters drain one kidney (incidence 1 : 150).
- Duplications may be incomplete (“Y” ureter) or complete:
- Orthotopic ureter:
- drains lower pole and enters bladder near trigone
- Ectopic ureter:
- drains upper pole and enters bladder inferiorly and medially (Weigert-Meyer rule);
- the ectopic ureter may be stenotic and obstructed.
- Orthotopic ureter:
-
Complications
- Reflux in orthotopic ureter, causing urinary tract infection (UTI)
- Obstruction of ectopic ureter
- Ureterocele
- Uterocele. A reformatted coronal image from a CT urogram demonstrates a partially duplicated collecting system on the left side with two ureters (black and white arrows) that join at the pelvic inlet and insert as one ureter into the bladder. At the insertion of the ureter, there is a saccular collection of contrast with a halo of lucency surrounding it characteristic of a ureterocele.
- http://www.learningradiology.com/notes/gunotes/ureterocoelecorrect.htm
•
- Nephroptosis
- AKA
- (floating or wandering kidney):
- Intro
- acquired condition with excessive descent of the kidney in erect position;
- differs from congenital pelvic kidney in that the paired renal arteries arise from their typical anatomic location.
- Definition
- descent of the kidney more than 5 cm or two vertebral bodies when the patient moves from a supine to upright position during IVU 1,2.
- Displacement can also occur medially across the midline, so-called medial nephroptosis 8,9. A 2013 case report even demonstrated anterior displacement 10.
- Clinical presentation
- It may be present in up to 20% of young, slim females and is mostly asymptomatic 2.
- It is more often seen on the right side, in up to 20%, is bilateral.
- Symptoms
- may include flank pain on standing that is relieved on lying down, with the hypothesis being that movement of the kidney causes intermittent renal tract obstruction 1.
- Rarely it can cause intermittent nausea, vomiting, hypotension, oliguria and proteinuria, a syndrome known as Dietl’s crisis 5.
- It may occur in childhood as well 11,12.
- Radiographic features
- Intravenous urography, renal scintigraphy with various tracers, CT and ultrasound may all allow for the diagnosis (performed supine and upright, lateral decubitus in medial ptosis) 3,4,8,9.
- Colour Doppler ultrasound (CDI) with estimation of renal resistive index (RI) has been shown to be sensitive in detecting renal blood flow impairment and may thus aid in decision for laparoscopic nephropexy 3.
- Treatment and prognosis
- Laparoscopic nephropexy, usually reserved for cases with vascular and/or obstructive renal impairment, has been shown to be successful in relieving symptoms caused by renal compromise 3,6,7,12.
- Case courtesy of Dr Sami Elhinnawi, Radiopaedia.org, rID: 56632
SYNDROME
What are the different Subtypes of RCC and their Associated syndromes/Hereditary Subtypes?
What are the 3 complications of this condition?
Horseshoe Kidney
- The two kidneys are connected across the midline by an isthmus.
- This is the most common fusion anomaly (other fusion anomalies: cross-fused ectopia, pancake kidney).
- The isthmus may contain parenchymal tissue with its own blood supply or consist of fibrous tissue.
- Complications
- Obstruction, infection, calculus formation in 30%
- Increased risk of renal malignancies, especially Wilms tumor
- Increased risk of traumatic injury
Case courtesy of Dr Aditya Shetty, Radiopaedia.org. From the case rID: 27958
SYNDROMES
Re Tuberous Sclerosis describe the following:
Type of inheritance
Genes
Renal Findings
associated findings?
- INHERITANCE
- AD
- GENES
- TSC1,TSC2
- RENAL
- Bilateral renal cysts that vary in number and size;
- bilateral angiomyolipomas
- (may not contain appreciable fat at imaging)
- renal cell carcinoma (rare)
- HEART
- Cardiac rhabdomyomas;
- CNS abnormalities
- (eg, corti-cal tubers,
- subependymal nodules,
- subependymal giant cell astrocytoma);
- ABDO
- hepatic angiomyolipomas;
- pancreatic neuroendocrine tumors;
- LUNGS
- lymphangioleiomyomatosis;
- multifocal micronodular pneumocyte hyperplasia;
- BONES
- osseous sclerotic lesions (bone islands);
- VESSELS
- (eg, abdominal aorta aneurysms)
Septum of Bertin (upper pole 90%, bilateral 60%); associated with bifid renal pelvis
Case courtesy of Dr Hani Makky Al Salam, Radiopaedia.org, rID: 9780
CT PROTOCOL
Kidney/Ureters
Hematuria Protocol
What is the single bolus CT technique for haematuria?
CT Protocols of the Kidney/Ureters
Hematuria Protocol
Single bolus CT technique
- Phase 1: Noncontrast CT of the abdomen and pelvis, including KUB
- Single bolus (100–150 mL, 300–320 mg of iodine/mL) of IV contrast material at 2–4 mL/s
- Early images of kidney in nephrographic phase
- Excretory phase images (5 min following injection) through KUB
Persistent fetal lobulation: scalloped appearance of renal outline; adjacent calyx is normal
Case courtesy of Dr Chris O’Donnell, Radiopaedia.org, rID: 41364
Junctional parenchymal defect:
- fusion defect in upper pole of kidney that does not represent a scar;
- echogenic linear defect extends from sinus;
- commonly seen in pediatric patients
Case courtesy of Dr Amir Rezaee, Radiopaedia.org, rID: 43561
KIDNEY ANATOMY
What comprises the renal collecting system?
Collecting System
- Minor calyces: most kidneys have 10–14 minor calyces.
- Major calyces
- Renal pelvis: may be completely within the renal sinus or partially “extrarenal.”
Inverted Papilloma
• No malignant potential
• 20% are associated with uroepithelial malignancies elsewhere, most commonly in bladder.
- General Information
- It is generally considered a benign histologic lesion; however, it may harbor malignant change.
- Median age is 55.
- Frequently presents with hematuria.
- Imaging
- Intravenous Pyelography
- Solitary solid, sessile or pedunculated, polypoid lesion
- Ultrasonography
- Echogenic mass within the ureteral lumen resulting in partial or complete urinary tract obstruction
- Computed Tomography
- Hypodense mass seen as filling defect in ureteral lumen. Delayed phase images at CT urography may clearly demonstrate.
- Intravenous Pyelography
- Pathology
- Inverted papilloma is more common in the ureter than the renal pelvis. It is also more common in older males.
- Inverted papilloma consists of typical urothelium that forms trabeculae which undermine the overlying mucosa. It is morphologically similar to its counterpart in the bladder.
- Differential Diagnosis
- Benign and malignant neoplasms of ureter, radiolucent stones, and blood clot
-
Pearls and Pitfalls
- Inverted papillomas of the renal pelvis and ureter may be associated with urothelial neoplasms elsewhere in the urothelial tract.
- Urothelial carcinomas may coexist with or arise within inverted papillomas.
- Inverted papillomas may recur.
- https://radiologykey.com/neoplasms-of-the-renal-pelvis-and-ureter-2/
- https://www.urotoday.com/recent-abstracts/urologic-oncology/bladder-cancer/108694-inverted-papilloma-a-rare-and-benign-cause-for-upper-urinary-tract-neoplasia.html
PATHOLOGY
What are the most common malignant and benign tumours of the renal pelvis?
Which is more common overall?
Renal Pelvis Tumors
Most tumors arising from the renal pelvis are malignant with transitional cell cancer being the most common tumor.
Papillomas are the most common benign tumor.
-
Case Discussion TCC
- Gross pathological sample
- Nephrectomy ( cut ).
- Large tumour occupying the renal pelvis extending into the upper and mid pole calyces.
- Transitional cell carcinoma is more commonly associated with the bladder, but can effect any part of the genitourinary tract.
- In this case it was identified on a CT performed for other purposes.
- Haematuria is the main symptomatic presentation.
- Imaging of the upper tracts is best undertaken with either CT-IVU or split bolus technique imaging.
- Images courtesy of Department of Pathology, RIPAS Hospital, Brunei.
- Case courtesy of Dr Ian Bickle, Radiopaedia.org, rID: 28184
Cross-fused ectopia: the ectopic kidney is inferior
Case courtesy of Dr Ahmed Abdrabou, Radiopaedia.org, rID: 32283
PROCEEDURE
What is a retrograde Pyleogram?
Retrograde Pyelogram
A catheter is placed in the distal ureter via cystoscopy and contrast is administered via the catheter by hand injection to opacify the collecting system (no parenchymal opacification).
This technique is primarily used for percutaneous ureterolithotomy (PUL) access and difficult nephrostomy placements.
Lobar dysmorphism:
- abnormally oriented lobe between upper and middle calyces;
- always points to posterior calyx,
- which is key to diagnosis on CT or IVP.
- By US this entity is indistinguishable from column of Bertin.
https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1442-2042.1995.tb00456.x
Simple cysts are found in ? amount of the pop over 50 yo.
They communicate with the collecting system. True or false?
Simple Cysts ( Fig. 4.3 )
- Simple cysts (in >50% of population >50 years) probably arise from obstructed tubules or ducts.
- They do not, however, communicate with the collecting system.
- Most commonly asymptomatic; rare findings include hematuria (from cyst rupture), hypertension (HTN), and cyst infection.
- Mass effect from large cysts may cause dull ache or discomfort.
CT PROTOCOL
Renal Mass Protocol
What are each of the phases for?
Renal Mass Protocol
Phase 1: noncontrast CT images of abdomen
Phase 2: corticomedullary phase, 25–30 s after contrast injection, through kidneys
Phase 3: nephrographic phase, 60–80 s after injection
https://radiopaedia.org/articles/renal-mass-protocol-ct?lang=gb
Terminology
For some departments and/or radiologists, a renal mass protocol may only include a non-contrast, nephrogenic phase exam. For others, it may consist of a corticomedullary phase (40-60 second delay) and/or an excretory phase (5-10 minute delay).
Indications
Indeterminate renal mass, renal adenocarcinoma, metastasis, monitoring of known renal mass.
Purpose
- The purpose of this exam is to assess the location and composition of a renal mass.
- non-contrast scan is best to determine the HU of homogenous renal mass or masses containing macroscopic fat 1
- corticomedullary phase is best to delineate subcategories of renal cell carcinomas further
- nephrogenic phase is best for optimal enhancement of the renal parenchyma, including the renal medulla, and will demonstrate enhancing components of a mass
excretory phase will demonstrate enhancement of calyces, renal pelvis and ureters. Many institutions will perform this around 5 minutes to demonstrate opacification of the ureters
Localized Cystic Disease
Benign, acquired unilateral condition characterized by multiple cysts of varying size.
Cysts, separated by normal renal parenchyma, may occupy the entire kidney or be more localized.
Calcification of cyst walls may be present but the cyst wall has to be thin; it does not compromise renal function.
No surgery necessary.
Radiographic features
Renal cysts in localised cystic renal disease can involve segments of the kidney or the entire kidney but are always unilateral. The key feature is that the cysts are separated by normal or atrophic renal parenchyma.
Unlike ADPKD, localised cystic renal disease is unilateral, and other organs do not have cystic involvement. In contrast to cystic nephroma, no capsule is seen around the cysts.
Case courtesy of Dr Huda B. Gharbia, Radiopaedia.org, rID: 61807
Case Discussion
There are numerous cystic lesions in the left kidney. They appear slightly hyperintense on T1W images, and show dark signal in T2W images, with show no signal loss T1 out phase sequences.
There are few cysts appear hypointense T1W and hyperintense in T2W images.
Hyperattenuating lesions relative to renal parenchyma and T2W markedly hypointense signal, with invisible fat content denoting blood or proteinatious content cysts with others few simple cysts, suggestive of localised renal cystic disease.
Drip-Infusion Nephrotomogram
What is it?
What are the steps?
Drip-Infusion Nephrotomogram
With drip infusion, the nephrogram persists longer, allowing more time for nephrotomography and special views, if necessary. Today, this is much less commonly performed than the bolus technique or computed tomography (CT). If calcifications are seen on the renal outlines, scout oblique radiographs can be obtained to determine the exact location relative to the kidneys.
Technique
- KUB and preliminary tomogram of kidneys (starting at 8 cm from back)
- Drip infusion of 300 mL of Urovist 14% (or Conray-30) or 150 mL of Isovue 300 (or Omnipaque 300)
- Obtain tomograms after 150 mL has been given. Usually 7 to 9 cuts are obtained.
- Postinfusion KUB and both oblique views
- Coned bladder view
- Postvoid KUB
PROCEEDURE
IVP
What are the indications?
What is the technique?
Bolus IVP
Today, IVPs are rarely used, but are covered for historical purposes.
The bolus administration ensures maximum concentration of contrast media in the kidney.
Indication: healthy ambulatory patients (screening type urography [e.g., for urinary tract infection (UTI)]), trauma.
Technique
- Kidney, ureter, bladder (KUB)
- Inject 100 mL of 30% contrast
- 1-min and 5-min radiograph of both kidneys
- 10-min KUB and both obliques
- Coned bladder view
- Postvoid KUB
Case courtesy of Dr Mohammad Taghi Niknejad, Radiopaedia.org, rID: 85286
What is this condition?
Who does it happen to and over what time period?
Associations?
Uremic Cystic Disease (UCD)
AKA: Aquired renal cystic disease (ARCD)
- 40% of patients with end-stage renal disease develop renal cysts.
- Incidence increases with time on dialysis so that incidence of UCD is 90% in patients on dialysis for 5 years.
- Associated complications include:
- Increased incidence of RCC
- Hemorrhage of cysts
- Cysts can regress after successful transplantation.
FIGURE 5.25. ARCD with renal cell carcinoma. Multiple small cysts in a patient on long-term dialysis with small kidneys bilaterally. Unenhanced (A) and enhanced (B) CT of the abdomen images demonstrate a large enhancing left renal tumor.
FIGURE 5.26. Acquired renal cystic disease. Multiple renal cysts and a perinephric hematoma are identified on this contrast-enhanced CT scan.
https://radiologykey.com/renal-cystic-disease-3/
It is easier to examine the native kidneys with CT (Fig. 5.25) and MRI than with ultrasound. Multiple small cysts are seen by CT or MRI in virtually all patients with ARCD. Dystrophic calcifications are common in the renal parenchyma or cyst walls. Bleeding is a common complication, so hemorrhagic cysts and subcapsular or perinephric hematomas are often found (Fig. 5.26). Carcinomas are seen as masses with a density similar to the unenhanced parenchyma. If large (<3 cm), the masses may be heterogeneous on enhanced images (Fig. 5.27).
What are the Imaging features of this condition?
Autosomal Dominant Polycystic Kidney disease
Imaging Features
- Kidneys are enlarged and contain innumerable cysts, creating a bosselated surface.
- Calcification of cyst walls is common.
- Pressure deformities of calyces and infundibula
- IVP: “Swiss-cheese” nephrogram
- Cysts have variable signal characteristics.
- CT: hypodense, hyperdense (hemorrhage, protein, calcium)
- T1-weighted (T1W): some cysts contain clear, watery fluid (hypointense); others contain blood and protein (hyperintense); layering in some cysts is caused by cellular debris.
- Hepatic cysts
Describe the Classification System of Renal Cysts
Bosniak Classification
- Category 1:
- benign simple cyst
- Simple cysts contain low-attenuation (0–20 HU) fluid and a hairline-thin smooth wall.
- Cysts do not contain septations, calcifications, or enhancing nodular soft tissue.
- Category 2:
- minimally complicated cysts that are benign but have certain radiologic findings of concern.
- Includes septated (paper-thin septations) cystic, minimally calcified cysts, high-density cysts.
- Fine calcification or a short segment of slightly thickened calcification may be present in the wall or septa.
- Hyperattenuating cysts contain more fluid than water attenuation (i.e., >20 HU).
- In general, cysts that measure between 20 and 40 HU are proteinaceous cysts and will show findings of a simple cyst using US;
- those with attenuations over 40–50 HU are likely to be hemorrhagic cysts and will be complex under US.
- When a hyperattenuating renal mass is encountered on an unenhanced CT scan, the probability of the mass being benign is more than 99% as long as the attenuation is 70 HU or more and the mass is homogeneous.
- Category 2F
- (the “F” means to follow)
- lesions cannot be considered benign without some period of observation.
- Slightly more complicated (e.g., may contain multiple, hairline-thin septa that demonstrate perceived [not measurable] enhancement).
- May have minimal smooth thickening of the wall or septa.
- May contain thick irregular or nodular calcification.
- No enhancing soft tissue components.
- Hyperattenuating renal masses that exhibit all the features of hyperattenuating cysts but are larger than 3 cm and are completely intrarenal are also included in this category.
- Recommended follow-up is to perform a CT or MR examination at 6 months, followed by yearly studies for a minimum of 5 years.
- Category 3:
- complicated cystic lesions that exhibit some radiologic features seen in malignancy
- This category includes
- multiloculated cystic nephroma,
- multiloculated cysts,
- complex septated cysts,
- chronically infected cysts,
- heavily calcified cysts, and
- cystic renal cell carcinoma (RCC).
- Because these entities are difficult to separate radiologically, surgery is usually performed.
- Category 4 lesion:
- clearly malignant lesions with large cystic component.
- Irregular margins, solid vascular elements
Urothelial Papilloma
Background: Epithelial Tumors of the renal sinus
Benign epithelial tumors are urothelial papilloma and inverted papilloma, which are extraordinarily rare and detected incidentally. Malignant epithelial tumors account more than 90 % of all renal pelvis and ureteral tumors. Approximately 90 % of malignant tumors are urothelial carcinomas (transitional cell carcinomas), followed by squamous cell carcinoma (10 %) and adenocarcinoma (less than 1 %).
Benign Epithelial Tumors:
- Urothelial Papilloma
- General Information
- Benign exophytic papillary urothelial tumor
- Tends to occur in younger patients
- Usually presents with gross hematuria
- Imaging
- Intravenous Pyelography
- Radiolucent filling defect in continuity with the wall of the collecting system
- Ultrasonography
- Echogenic focus within the ureter and renal pelvis associated with the moderate to severe hydronephrosis
- Computed Tomography
- A ureteral or renal pelvis mass with attenuation in the soft-tissue range of 30–40 Hounsfield units
- Magnetic Resonance Imaging
- Magnetic resonance urography demonstrates the localization and extent of tumor by showing hypointense filling defect in renal pelvis and ureter on heavily T2-weighted images.
- Intravenous Pyelography
- Pathology
- Urothelial papilloma in these sites is rare. It is a mucosal lesion composed of a delicate papillary frond lined by typical urothelium of normal thickness. It is morphologically similar to its counterpart in the urinary bladder.
- Differential Diagnosis
- Papillary neoplasm of low malignant potential is a papillary urothelial neoplasm. Mean age of this disease is 64.6 years.
- Transitional cell carcinoma, blood clots, and fungus balls.
- Pearls and Pitfalls
- Urothelial papilloma tends to occur in younger patients.
- MR urography may show benign characteristics of this tumor by demonstrating the absence of periureteral or perirenal invasion.
- https://www.ajronline.org/doi/pdf/10.2214/AJR.14.13879
- https://radiologykey.com/neoplasms-of-the-renal-pelvis-and-ureter-2/
?recurrence rate
?% with lung mets?
%with bladder findings?
how many % have this in bladder and later devcelop this pathology?
Renal pelvis Transitional Cell Carcinoma
- Tumors are often multifocal: 40%–80% of patients have bladder TCC. However, only 3% of patients with bladder TCC later develop upper tract TCC.
- Radiographic finding: irregular filling defect
- Obliteration of renal sinus fat and infiltration of renal parenchyma (faceless kidney)
- 60% recurrence on ipsilateral side
- 50% have lung metastases.
Case courtesy of Dr Ian Bickle, Radiopaedia.org, rID: 25450
What is this Syndrome?
What needs to be excluded?
Wunderlich syndrome.
Case Discussion
- Predominantly echogenic lesion involving the upper pole of the right kidney associated with more complex appearing perinephric collection.
- CT scan of the abdomen confirms the presence of a fatty lesion in the upper pole of the right kidney consistent with angiomyolipoma complicated by haemorrhage.
- Incidental two tiny hepatic haemangiomas.
- Perirenal haemorrhage without a history of trauma complicating an angiomyolipoma is known as Wunderlich syndrome.
- If perirenal haemorrhage is encountered on ultrasound, a thorough workup should be performed to exclude a bleeding renal cell carcinoma.
- Case courtesy of Dr Hani Makky Al Salam, Radiopaedia.org, rID: 10090
What is a Ureteral spindle?
Ureteral spindle: dilatation of middle third of ureter at crossing of iliac vessels
CT PROTOCOL
Split bolus CT technique:
what is it used for?
Why?
Split bolus CT technique:
- Phase 1: noncontrast CT of abdomen and pelvis. Immediately thereafter administer 30 mL of IV contrast and wait 5–10 min.
- Phase 2: place patient back on scanner and inject 100 mL of contrast at 2–3 mL/s, and scan patient prone from top of kidneys to pubic symphysis after 100 s.
- Phase 2: excretory phase (5 min) through the kidneys is obtained at the same time as the 100-s scan. The initial bolus of 30 mL should now be making its way through the collecting system.
https://radiopaedia.org/articles/split-bolus-technique
The split bolus technique is a CT imaging investigation used in patients with haematuria aiming to put together, in a single image acquisition, both the nephrographic and renal excretory phases and thus reducing the radiation dose of the study. It is a CT protocol adopted for some institutions for assessing a patient with haematuria 1,2.
Usually, a prior unenhanced study of the abdomen and pelvis in the form of a CT-KUB has been performed or undertaken before the split bolus component, excluding nephrolithiasis as the cause of the haematuria. Then, the patient receives 50 mL of IV contrast followed by an additional 50 mL eight minutes later. Images are then acquired 55 seconds following the second dose of IV contrast. In some centres the patient may be asked to lie in a prone position.
This provides contrast imaging of the kidneys to look for a renal mass, such as renal cell carcinoma along with a CT-IVU, allowing for the detection of upper tract disease, such as transitional cell carcinoma. Bladder images are acquired which are insightful, but this should not be a substitute for cystoscopic assessment.
The technique has been shown to have a high sensitivity, specificity and accuracy for detecting upper tract tumours 3.
Case courtesy of Dr Ian Bickle, Radiopaedia.org, rID: 60355
Presentation
- Right upper quadrant acute pain and tenderness.
- Hyperechogenic lesion with sharp borders.
- A round lesion with fat density (-75 HU) and only minimal focal enhancement.
- Case courtesy of Dr Roberto Schubert, Radiopaedia.org, rID: 16842
- Case Discussion
- Mixed fat-solid vascularised giant mass in the renal space with central foci measuring around 40 HU - probable haematoma. Note additional small fat foci in both kidneys and one small focus in the liver.
- Mass and right kidney were removed.
- Histology report (summary)
- Angiomyolipoma growing out of the renal cortex, tumour cells were mildly pleomorphic, without mitosis or necrosis. MDM-2 negative. Additional small foci of angiomyolipomas in the kidney.
- Case courtesy of Dr Igor Strahovnik, Radiopaedia.org, rID: 31532
- Contributor: Dr Mitja Četina
Aberrant papilla:
- papilla indents infundibulum or pelvis rather than minor calyx
- Figure 18-6 Frontal image of the left kidney from an intravenous urogram demonstrating an aberrant renal papilla in the lower pole infundibulum.
https://radiologykey.com/kidneys-4/
What are the imaging features of this pathology?
IVP
CT
US
MRI
Simple renal cyst
Imaging Features
- IVP
- Lucent defect
- Cortical bulge
- Round indentations on collecting system
- “Beak sign” can be seen with large cysts.
- US
- Anechoic
- Enhanced through-transmission
- Sharply marginated, smooth walls
- Very thin septations may occasionally be seen.
- CT
- Smooth cyst wall
- Sharp demarcation from surrounding renal parenchyma
- Water density (<10–15 HU) that is homogeneous throughout lesion
- No significant enhancement after IV contrast administration (small increases of <5 HU, however, can be seen likely due to technical factors, not true enhancement)
- Cyst wall too thin to be seen by CT (with small cysts, volume-averaging may create the false appearance of a thick wall)
- MRI
- Indications (rather than CT):
- renal insufficiency,
- solitary kidney,
- contrast allergy,
- patients with complex cystic renal masses needing multiple follow-up examinations
- End-expiration images are preferred because they are more reproducible in optimizing image coregistration and subtraction algorithms if the patient can hold his or her breath.
- Simple renal cysts are uniformly hypointense on T1W and hyperintense on T2W images with no perceptible enhancement after gadolinium. MRI can characterize extremely small renal cysts.
- Internal components of cystic masses and subtle enhancement are better appreciated by MRI than by CT
- Indications (rather than CT):
Case courtesy of Dr Ian Bickle, Radiopaedia.org, rID: 83652
Sinus lipomatosis:
- large amount of fat in renal sinus
- It results from renal parenchymal atrophy, inflammation, calculous disease, ageing, or exogenous or endogenous steroids.
- There is usually no or rarely little mass effect on the collecting system.
- Variants
- replacement lipomatosis of the kidney: an advanced massive form of renal sinus lipomatosis, in which infection, renal calculi, and long-standing hydronephrosis are accompanied by severe renal parenchymal atrophy; might be with mass effect causing attenuation and stretching of the collecting system
Differential diagnosis
- Possible differential considerations include:
- xanthogranulomatous pyelonephritis: on ultrasound
- fat-containing renal tumours
- renal angiomyolipoma
- renal lipoma
- renal liposarcoma
Case courtesy of Dr Khalid Alhusseiny, Radiopaedia.org, rID: 91277
Linear vascular impressions on renal pelvis and infundibula
https://www.ajronline.org/doi/pdf/10.2214/ajr.101.3.719
Parapelvic Cyst
- Originates from renal parenchyma but expands into the renal sinus
- May cause compression of the collecting system
- Case Discussion
- The left kidney showed renal sinus cyst stretching and displacing pelvicalyceal system which is minimally dilated as compared to the right kidney.
- A parapelvic cyst at times may cause compression of the pelvicalyceal system resulting in hydronephrosis. Parapelvic cyst can mimic hydronephrosis and so can be confused with pelvi-ureteric junction obstruction as the ureter in both conditions is not dilated. This could be well differentiated at the excretory phase of CT-IVP study (CT urography) that demonstrates stretched (but not dilated) collecting system by the cyst in contrary to PUJ obstruction at which the contrast will be excreted inside the dilated pelvicalyceal system. It can cause pelvicalyceal system dilatation by its mass effect.
- Case courtesy of Dr Mostafa El-Feky, Radiopaedia.org, rID: 52815
What is the work up for the different classifications of renal cysts?
