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FUNDAMENTALS OF BODY CT > Kidneys And Ureters > Flashcards

Kidneys And Ureters Flashcards

1
Q

CT protocol for renal masses

A
  1. Non contrast phase
  2. Corticomedullar phase (30 sec)
  3. Nephrogram phase (80-90 sec)
  4. Pyelogram phase (3-5 mins).
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2
Q

CT urogram protocol

A
  1. Non contrast phase
  2. Nephrogram phase (80 sec)
  3. Pyelogram phase (5-8 mins)
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3
Q

Horshoe kidney

A

congenital fusion of lower poles, 1/400 births, isthmus across the aorta below IMA, multiple abnormal renal arteries, urinary stasis, causes: stone formation, recurrent infection, x3-4 increased risk of TCC

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4
Q

Renal Masses important features

A
  • Presence and type of calcifications
  • Attenuation before and after contrast
  • Margins with kidney and surrounding tissues,
  • Prescence and thickness of wall septa and cystic masses.
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5
Q

Increase of attenuation of renal masses in UH in order to be significant

A

Beam hardening effect may increase attenuation of lesions by up to 10 UH

Therefore:

Enhancement: >20 UH
Equivocal enhancement: 10-20 UH
Non enhancement: <10 UH

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6
Q

Renal cell carcinoma types (6)

A

Clear cell, multilocular cystic RCC, papillary (Chomophil), chromophobe, hereditary cancer syndromes and others.

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7
Q

Clear cell RCC

A

70% RCC, heterogeneous (solid, cystic, foci of hemorrage and necrosis), hypervascularity (>84 UH, remains high), expansile growth, 5% bilateral

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8
Q

Multilocular cystic RCC

A

Variant of clear cell RCC, clusters of cysts, fibrous capsule and septa (20% calcified), slower growth and less metastases/recurrence

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9
Q

Papillary RCC (Chromophil)

A

10-15% RCC, from distal convoluted tubules, homogenous solid tumors (may be cystic), hypovascular. When large: hemorrage, necrosis and calcifications, 70% confined to the kidney, good prognosis with surgery

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10
Q

Chromophobe RCC

A

5% of RCC, from collecting duct cells, ultrasound: hyperechoic (similar to AML), Typically homogeneous enhacement, but may have: central scar, necrosis, calcifications, spoke-wheel pattern, good prognosis.

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11
Q

Hereditary cancer syndromes (renal)

A

5% of RCC
Early and bilateral development of RCC.
Von hippel lindau: Clear cell RCC
Birt hogg dube: Chromophobe RCC

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12
Q

Rare cell types of RCC

A

<1% of RCC
Renal medullary carcinoma: <40 years with sickle cell trait
Collecting duct RCC
Mucinous tubular and sprindle cell RCC
Traslocation (juvenile) RCC

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13
Q

Suspicion criteria for benign kidney solid masses

A
  1. Homogeneous lession <20 or >70 UH
  2. Size <3 cm (20% benign: oncocytoma, AML, papillary adenoma, metanephritic adenoma)
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14
Q

RCC signs of invasion

A
  • Tumor growth into the main renal vein (20-35%) and IVC (4-10%)
  • Filling defects in the collecting system
  • Regional lymphnodes >2 cm is almost always a metastasic tumor
    (1-2 cm are indeterminate)
  • Metastases: Lung, liver and bone
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15
Q

Recurrence of RCC

A
  • Usually <6 years after surgery.
  • Local recurrence in the renal fossa 5%.
  • Lymphatic recurrence in nodes close to the renal vascular pedicle.
  • Late metastases >10 years: Lung, pancreas, bone, skeletal muscle and bowel.
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16
Q

Renal Oncocytoma

A

Benign solid tumor, arises from proximal renal tubule, men 60s, 5% of renal neoplasms, no test can reliably differenciate from RCC, treatment is surgical

CT findings:
- Solitary, well-defined, arises from the cortex, Homogeneous attenuation after contrast
- Central, stellate, sharply marginated low attenuation central scar (33% of tumors)
- Inverted segmentary enhancement
- Can also be: heterogeneous attenuation, necrosis, hemorrage

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17
Q

Renal Angiomyolipoma Generalities

A
  • Most common benign renal tumor.
  • Angio: Might have aneurysms, high risk of hemorrage > 4 cm.
  • Lipo: Pockets of fat <-10 UH is specific for AML (95%) (5% of AML are lipid-poor).
  • CT findings: Cortical, well-marginated, solid and fat containing lesion.
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18
Q

Renal Angiomyolipoma common presentations (2)

A
  1. Sporadic and solitary (80-90%): Middle aged women
  2. Multifocal and bilateral (10-20%): Tuberous sclerosis
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19
Q

Lipid poor renal Angiomyolipoma vs RCC

A
  • RCC often show other signs of malignancy.
  • Intratumoral calcifications are never present in AML.
  • AML has high attenuation on unhanced CT and show homogeneous increased attenuation on enhanced CT.
  • Biopsy is usually required to differenciate them.
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20
Q

Renal Angiomyolipoma and tuberous sclerosis

A
  • Multiple AML are found in both kidneys (80%).
  • Multiple renal cysts (50%).
  • AML are large and with high risk of hemorrage.
  • 2-3% develop RCC at young age (average 28 years old).
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21
Q

Transitional cell carcinoma - Generalities

A
  • 90% from the bladder, 10% from the upper tracts.
  • Aditional TCC may be present synchronously.
  • Most ureteral uroepithelial tumors (>70%) occur in the distal ureter.
  • They appear as filling defect or circumferential thickening of the wall of the ureter.
  • Calcifications might mimic lithiasis (5%).
  • Advanced TCC might invade renal sinus fat, renal parenchyma, extrarenal extension, regional lymphnodes, metastases to lungs and bone.
  • Rarely: invation of renal vein and IVC.
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22
Q

Transitional cell carcinoma - Upper tract Locations

A
  1. Filling defects in the renal pelvis (35%).
  2. Filling defects within dilated calyces (26%).
  3. Thickening of the wall of the renal pelvis (20%).
  4. Abscent or decreased contrast medium excretion (13%).
  5. Diffuse hydronephrosis with renal enlargement (6%).
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23
Q

Renal lymphoma Generalities

A
  • Usually systemic disease, B-Cell non-Hodgkin and Burkitt lymphomas are the most common.
  • Abscense of involvement of retroperitoneal nodes excludes lymphoma as a cause of renal mass.
  • Tumor encasement of the renal artery and vein hardly ever produces thrombosis.
  • Biopsy needed to confirm diagnosis.
  • CT findings: 1-3 cm, homogeneous hypo-dense, no margins, hypovascular lesion.
  • Presentation: Solitary, perirenal, contiguous, multiple or diffuse.
24
Q

Metastases to the kidneys

A
  • Most common: Lung, breast, GI adenocarcinomas.
  • Multiple bilateral low-attenuation renal nodules (most common).
  • Isolated solitary metastases (commonly seen with colon cancer and melanoma).
  • Diffusely infiltrative metastases (uncommon).
  • Ocasionally the kidney might be the only site of metastases.
25
Q

Papillary adenoma of the kidneys

A
  • Small <5 mm solid renal mass
  • Arises from epithelium of renal tubules
  • Solitary, subcapsular in location
  • > 5 mm are considered carcinomas
26
Q

Metanephritic Adenoma

A
  • Very rare benign tumor, no malignant potential. No treatment needed
  • CT: Solitary well-defined solid mass with attenuation higher than the rest of the parenchyma, hypovascular, limited enhancement
  • Usually 5 cm, larger sizes are heterogeneous, can have hemorrage, necrosis and calcifications (20%), biopsy needed
27
Q

Cystic Renal Masses Types (7)

A

1) Simple Cysts
2) Renal Abscess
3) Multicystic RCC
4) Mixed Epithelial and Stromal Tumor
5) Multilocular cystic Renal Tumor
6) Localized Renal Cystic Disease
7) Small indeterminate Renal Mass

28
Q

Bosniak Classification

A

Bosniak Classification:
- Category I: Benign simple cyst
- Category II: Benign complicated cyst
- Category IIF: Follow-up
- Category III: Indeterminate cystic lesions
- Category IV: Malignant cystic tumors

29
Q

Simple renal Cysts

A
  • Benign, non-neoplastic, fluid-filled masses.
  • Multiple-bilateral cysts are common (>55 years old 50% have them).
  • CT findings: Homogeneous, near water density,sharp margination, no walls, +30 UH maximum enhancement.
  • Homogeneous RCC have attenuation values no lower than +42UH on postcontrast CR.
30
Q

Renal Abscess

A
  • CT appear as thick-walled, low attenuation collections within the renal parenchyma, it’s wall enhances with contrast
  • Gas is sometimes present
  • Septations might be thick and irregular.
  • Extension of infection into the perirrenal space is common
31
Q

Cystic or Multicystic RCC

A
  • Some clear cell RCC are composed of multiple fluid-filled noncommunicating cystic spaces
  • Cystic forms of papillary RCC appear as cystic mass with enhancing papillary projections or enhanced solid components
  • RCC + adjacent simple cyst
32
Q

Mixed Epithelial and Stromal Renal Tumor

A
  • Rare, complex cystic and solid masses.
  • Perimenopausal women (11:1).
  • Stromal elements resemble ovarian stroma.
  • Indistinguisable from cystic RCC.
33
Q

Multilocular cystic Renal Tumor (Cystic nephroma)

A
  • Uncommon benign renal neoplasm composed of cysts of various sizes separated by connective tissue septa.
  • 2/3 in males between 2 months and 4 years // The rest women 40-60 years old.
  • CT findings:
  • Solitary upper pole mass, multiple fluid-filled locules 1-25 mm, septa enhances moderately but less than RCC.
  • Necrosis, hemmorrhage and calcifications are rare.
  • Treatment is surgical excision.
34
Q

Localized Renal Cystic Disease

A
  • Benign condition that resembles multilocular cystic nephroma
  • Multiple simple cysts of various sizes are separated by normal enhancing renal parenchyma
  • No discrete encapsulation is present
  • Other, clearly separated, benign cysts are found nearby
  • Commonly affects only one portion of the kidney // might affect the entire kidney
  • No other cysts in other organs
35
Q

Small indeterminate Renal Mass

A
  • Most small renal masses are simple cysts.
  • In asymptomatic low-risk patients, lesions smaller than 10 mm are assumed to be benign cysts
  • In high risk patients (VHL, family history of RCC, acquired renal cystic disease of hemodialysis), the urologist may choose surgical excision.
  • CT follow up at: 3 or 6 months for 1 year is an option.
  • Percutaneous image-guided renal mass biopsy is also an option.
36
Q

Multiple Renal Simple Cysts

A

Simple cysts increase in frequency with age and are commonly multiple and bilateral

37
Q

Autosomal Dominant Polycystic Kidney Disease

A
  • The cortex and medulla of both kidneys are progresively replaced by multiple noncommunicating cysts.
  • Most present clinically with hypertension and renal failure at the age of 30-50 years.
  • Renal cysts are commonly complicated by bleeding or infection
  • Cysts are present in other organs, liver 30-50% and pancreas 10%
  • Cysts may have calcified walls and high internal attenuation due to hemorrage, infection, inflammation or ischemia
  • Renal stones are common (20-40%)
38
Q

Autosomal Recessive Polycystic Kidney Disease

A
  • Usually detected by ultrasound in the uterus.
  • Present at birth with severe renal funcion impairment.
  • Ectasia and cystic dilation of the renal tubules involving both kidneys.
  • Associated with congenital hepatic fibrosis, portal hypertension, bile duct ectasia and Caroli disease.
39
Q

Multicystic Dysplasic Kidney

A
  • Non hereditary renal dysplasia, the kidney consists of multiple, thin-walled cysts held together by connective tissue
  • Due to high grade urinary tract obstruction during embryogenesis
  • Child-hood and early adulthood: kidney as non functioning multiloculated cystic mass
  • Older: Kidney shrinks and becomes calficied
40
Q

Renal Von-Hippel-Lindau Disease

A
  • Rare autosomal dominant disorder.
  • Cerebellar, spinal cord and retinal hemangioblastomas, renal and pancreatic cysts, RCC and pheocromocytoma.
  • Multiple renal bilateral cysts present in 50-75%.
  • RCC occurs in 28-45%: Solid, multicentric and bilateral, some as complex cyst with enhancing septa. Most are clear cell carcinoma.
  • Pheocromocytoma 30% of cases, bilateral 50%, malignant 10-15%.
41
Q

Renal Tuberous Sclerosis

A
  • Autosomal Dominant syndrome, multiple renal cysts (50%) + bilateral AML (75%).
  • Seizures, mental retardation, adenoma sebaceum.
  • Cutaneous, cerebral, retinal, cardiac hamartomas.
  • 60% no family history (sporadic).
  • 40% dies at 35 years old.
  • Might associate with “Retroperitoneal lymphangioleiomyomatosis”.
42
Q

Acquired Renal Cystic Disease

A
  • Long term hemodialysis, >90% of patients develop innumerable cysts in both kidneys after 5-10 years
  • Complicated by hemorrages and development of RCC (3-7%)
  • Cysts are <6 mm, up to 2 cm, might have blood and calcium and calcified walls
43
Q

Acute Bacterial Pyelonephritis CT findings

A
  • Wedge-shaped areas of mottled decreased parenchymal enhancement
  • Striatted pattern of linear alternating increased and decreased attenuation (Striatted Nephrogram)
  • High-attenuation areas of parenchyma on unenhanced CT (areas of hemmorage)
  • Stranding densities in the perirrenal fat and thickening of the renal fascia
  • Poorly defined mottled low-attenuation mass withoud dinstinct liquefaction (lobal nephronia, focal pyelonephritis, etc.)
44
Q

Emphysematous Pyelonephritis

A
  • Severe life threatening necrotizing type of diffusing pyelonephritis.
  • Diabetes (90%), immunocompromised patients and urinary tract obstruction.
  • CT shows gas in the renal parenchyma.
  • Emergency nephrectomy may be required.
45
Q

Pyonephrosis

A
  • Acute infection with pus within an obstructed collecting system.
  • Contains high-attenuation fluid.
  • The wall of the collecting system is thickened >2 mm.
  • The renal parenchyma is often thinned. Intraparenchymal abscesses may be present.
  • Inflammatory changes surround the kidney and collecting structures.
46
Q

Renal Tuberculosis

A
  • The most common extrapulmonary site of infection (15-20% of cases).
  • Multiple caseous granulomas form in the renal cortex.
  • Usually unilateral
  • Calcifications within the renal parenchyma are a hallmark of the disease, present in 40-70%
  • Fibrotic strictures with wall thickening of the infundibula, pelvis and urether
  • Calyces are often dilated, filled with clear fluid, debris or calculi
  • Cortical thinning caused by scarring is usually present
47
Q

Xanthogranulomatous Pyelonephritis

A
  • Combination of chronic renal obstruction and chronic infection.
  • The renal parenchyma is progressively destroyed and replaced by lipid-filled macrophages
  • Staghorn calculus: Involvement of the entire kidney.
  • Solitary or indundibular calculus: Focal involvement.
  • CT findings:
    1) Low-attenuation enlargement of the entire kidney or the affected area.
    2) multiple low attenuation masses (dilated calyces).
    3) Kidney enhances but fails to excrete contrast.
    4) The obstructing calculus is visible.
    5) Obstructed calyces and intrarenal abscess.
    6) Extension of the infective process into the perirrenal tissues.
48
Q

Uretheral Duplication

A
  • The most common anomaly of the urinary tract (1% of the population).
  • Complete duplication: Weigert-Meyer rule
    1. Upper pole of the kidney has fewer calyces and it’s urether inserts the bladder medially and inferiorly (obstructs - uretherocele)
    2. Lower pole of the kidney is normal and it’s urether inserts normally into the bladder (Reflux due to the uretherocele)
  • When the duplication is incomplete, they fuse at a variable distance, yo-yo reflux occurs between the two urethers.
49
Q

Transitional Cell Carcinoma of the Urether

A
  • 90% of ureteral tumors
  • 75% occur in the distal part of the urether
  • 50% associated with bladder TCC
  • Tumor Growth patterns:
    1. Papillary: Filling defect in the dilated lumen of the urether.
    2. Infiltrating: Irregular wall thickening and scricture.
  • CT presentations:
    1) Soft tissue mass expanding and obstructing the urether.
    2) Irregular filling defect within high-attenuation urine .
    3) Irregular thickening of the ureteral wall.
50
Q

CT appearance of urinary stones

A

1) Calcium oxalate and phosphate (73%): 1200-2800 UH
2) Struvite stones (15%): 600-900 UH
3) Uric acid stones (8%): 200-450 UH
4) Cystine stones (4%): 200-1100 UH
5) Crystalline stones (Indinavir): 20-50 UH

51
Q

Acute Uretheral Obstruction CT findings

A

1) Stone demonstrated in the urether: Most common locations are ureteropelvic junction, pelvic brim and ureterovesical juncion
2) Size and location of the stone:
<4 mm almost always pass, 6 mm 50% pass, >8mm rarely pass
3) CT Signs of obstruction

52
Q

Common pitfalls in Diagnosis of Stones in the Urether

A
  1. An extrarenal pelvis may mimic pelviectasis.
  2. Peripelvic and parapelvic cysts may simulate hydronephrosis.
  3. Older patients might have preexisting stranding in the peripelvic fat.
  4. Preexisting postobstructive changes.
  5. Phleboliths might mimic stones.
  6. Recently passed stone.
  7. Other diagnosis: stricture, tumor, crystalline stones.
53
Q

Emphysematous Pyelitis

A
  • Gas confined to the renal pelvis and calyces.
  • Causes: Infection, trauma, instrumentation or fistula.
  • Lacks the dire implications of gas within the renal parenchyma.
54
Q

Renal Abscess

A
  • Collection of pus and liquified tissue within the kidney or with spread to the perirenal space
  • CT: Fluid collection (10-30 UH) with an enhancing rim, gas might be present
  • Usually require catheter or surgical drainage
55
Q

Putty Kidney (Riñon Mastic)

A

End stage renal tuberculosis: Extensive calcification of a nonfunctioning kidney

55
Q

Phleboliths vs urinary stones

A

Phlebolits differenciate by:
- Form: Round-oval and never geometric in shape.
- Location: Found in perivesical, periprostatic, periuterine and perivaginal veins.
- Tail sign: Non-calcified thrombosed vein extending from the phlebolith.
- CT density: Mean attenuation of 160 UH, never >300 UH.

55
Q

CT Signs of obstruction due to urinary stones

A

1) Tissue rim sign.
2) CT scout scan positive.
3) Enlarged and decreased density of obstructed kidney (>5 UH difference).
4) Periureteral and perinephric fat stranding.
5) Dilated urether and calyces.
6) Unilateral abscence of “white pyramids”.
7) Focal perinephric fluid collections due to rupture of the collecting system.

FUNDAMENTALS OF BODY CT (8 decks)

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