4. Genitourinary (Kidneys) Flashcards
Normal kidney anatomy (4)
Normal adult kidney is bean shaped, with smooth, oftem lobulated outer border.
Surrounded by thick capsule, outlined by perirenal fat.
Perirenal fat is continguous with the renal sinus, filling the middle of the kidney.
Cortex extends centrally into the middle of kidney, separated by less echogenic medullary pyramids.
Normal kidney is around 9-15cm in length.
Normal kidney - ultrasound (3)
Echogenicity should be equal to, or slightly less, than liver and spleen.
If renal echogenicity > liver, suggests impaired renal function.
Liver > kidney suggests fatty liver.
Fetal lobulation (3)
Anatomic variant.
Fetal kidneys are subdivided into lobes, separated with grooves.
Sometimes this lobulation persists into adulthood.
Fetal lobulation vs Scarring (2)
Lobulation: Renal surface indentations overlie the space between pyramids.
Scarring: renal surface indentations overlie medullary pyramids.
Dromedary hump (2)
Anatomic variant.
Focal bulge on left kidney, forms as a result of adaptation to adjacent spleen.
Prominent or hypertrophied column of Bertin (3)
Normal variant, hypertrophied cortical tissue located between pyramids results in splaying of the sinus.
Other than hypertrophy, looks and enhances normally.
Looks like big echogenic cortex on US.
Renal agenesis (4)
Congenital absence of one or both kidneys.
Unilateral can be asymptomatic.
- usually sporadic, but can be associaed with gynae abnormalities such as unicornate uterus
- in men, can be associated with absence of ipsilateral epididymis and vas deferens, or ipsilateral seminal vesicle cyst
Bilateral can cause Potter sequence.
Renal agenesis - associations (5)
Potter sequence
- Insult (maybe ACEi) > Kidneys don’t form > Can’t pass urine > Can’t develop lungs (Pulmonary hypoplasia)
Mayer-Rokitansky-Kuster-Hauser
- Mullerian duct anomalies including absence or atresia of uterus.
- Associated with unilateral renal agenesis
Lying down adrenal or “pancake adrenal” sign
- Elongated appearance of adrenal, not normally molded by adjacent kidney.
- Can differentiate surgically absent vs congenitally absent kidney.
Horseshoe kidney (8)
Most common fusion anomaly.
Complications include
- traumatic injury (gets crushed against vertebral body)
- UPJ obstruction
- Recurrent infection
- Recurrent stones
- Wilms tumour (8x increased risk)
- TCC due to infections
Also associated with
- Turners
- Renal carcinoid
Crossed fused renal ectopia (3)
One kidney comes across the midline and fuses with the other.
Ectopic Crossed Kidney is Inferior.
Left kidney more commonly crosses.
Complications include stones, infection and hydronephrosis.
Renal cell carcinoma - overview (8)
Commonest primary renal malignancy.
RCC until proven otherwise if:
- Enhances >15HU with contrast
- Calcifications in a fatty mass
Risk factors include
- Tobacco
- VHL
- Chronic dialysis (>3 years)
- Family Hx
Hypervascular mets, mets are always lytic when they met to bone.
Pseudoenhancement (2)
Less than 10HU is considered within technical limits of study and not necessarily enhancement.
More rare once a cyst is larger than 1.5cm
Fat in RCCs (3)
Clear cell most likely to have fat.
Fat containing lesion in the liver can be RCC met.
RCCs with macroscopic fat almost always have some calcification, otherwise it’s likely an AML.
RCC subtypes (8)
Clear cell
- most common, associated with VHL.
- More aggressive than papillary and will enhance equal to cortex on corticomedullary phase
Papillary
- second commonest. Less agressive than clear cell.
- Less vascular and will not enhance equal to corrtex on corticomedullary phase.
- T2 dark, along with lipid poor AML and haemorrhagic cysts.
Medullary
- Associated with sickle cell trait.
- Highly aggressive and usually large, usually already mets at time of diagnosis. Usually younger patients.
Chromophobe
- Associated with Birt Hogg Dube
RCC staging (7)
Stage 1 = Limited to kidney, >7cm
Stage 2 = Limited to kidney, >7cm
Stage 3 = Still inside Gerota’s fascia
Stage 3a = Renal vein invaded
Stage 3b = IVC below diaphragm
Stable 3c = IVC above diaphragm
Stage 4 = Beyond Gerota’s fascia, Ipsilateral adrenal
Polycystic Kidney Disease and RCC
APCKD doesn’t itself increase risk of RCC, but it does increase risk of needing dialysis, which increases RCC risk.
Renal lymphoma (4)
Can look like anything.
Most commonly bilateral enlarged kidneys with small, low attenuation cortically based solid nodules or masses.
Solitary mass in about 25%.
Lymphoma is most likely renal mass to preserve normal kidney shape
Renal leukaemia (3)
Kidney is commonest involved visceral organ in leukaemia..
Typically smooth, enlarged kidneys.
Hypodense lesions are cortically based only, with little medulla involvement if at all
Renal oncocytoma (4)
Second commonest benign tumour after AML.
Looks like RCC, but has central scar.
No malignant features (e.g. vessel infiltration).
Cannot be distinguished from RCC on imaging and must be treated as such until proven otherwise. (RCCs can also have the central scar)
Renal oncocytoma - imaging (3)
three ways it can appear
1) Solid mass with central scar on CT or MRI
2) Spoke wheel vascular pattern on USS
3) Hotter than surrounding renal cortex on PET
Birt Hogg Dube associations (2)
Associated with chromophobe RCC and bilateral oncocytomas
Multilocular cystic nephroma (4)
Non-communicating fluid filled locules surrounded by thick fibrous capsule.
Characterised by absence of solid component or necrosis.
Buzzword “protrudes into renal pelvis”
Bimodal occurence (4 year old boys and 40 year old women).
Bosniak cyst classification (5))
Class 1: Simple, <15HU, no enhancement.
Class 2: Hyperdense (<3cm). Thin calcifications, thin septations.
Class 2F: Hyperdense (>3cm), minimally thickened calcifications (5% cancer risk)
Class 3: Thick septations, mural nodule, 50% cancer risk
Class 4: Any enhancement (>15HU), 100% chance of cancer
Hyperdense cysts (2)
If >70HY and homogenous, it’s benign.
Usually haemorrhagic or proteinaceous cyst
ADPKD (4)
Kidneys get progressively larger and lose function, dialysis by 5th decade.
Hyperdense contents and calcified wall frequently seen due to prior haemorrhage.
70% get liver cysts too.
Associated with berry aneurysms.
ARPKD (5)
HTN and renal failure.
Liver involvement leads to abnormal bile ducts and fibrosis.
Congenital hepatic fibrosis is always present in ARPKD.
Ratio of liver and kidney disease is inversely related.
US: Kidneys are smoothly enlarged and diffusely echogenic, loss of corticomedullary differentiation.
Uraemic cystic kidney disease (3)
40% end stage renal disease pts develop cysts.
Rises with duration of dialysis, affects 90% of dialysis after 5 years.
Increased risk of malignancy with dialysis 3-6x.
Cysts regress after renal transplant
Von-Hippel Lindau (4)
AD, multi system disorder. 50-75% renal cysts, 25-50% get RCC
Pancreas: cysts, serous microcystic adenomas, neuroendocrine tumous (islet cell)
Adrenal: Phaeochromocytomas (often multiple).
CNS: Haemangioblastoma of the cerebellum, brainstem and spinal cord
Tuberous sclerosis (6)
AD, multisystem disorder.
Hamartomas everywhere (brain, lung, heart, skin, kidneys).
Renal: Bilateral multiple angiomyolipomas, cysts and occasionally RCC in younger people.
Lung - LAM (thin walled cysts and chylothorax)
Cardiac - Rhabdomyosarcoma, typically involves cardiac septum
Brain - Giant Cell Astrocytoma, cortical and subcortical tubers, subependymal nodules
Lithium nephropathy (4)
Long term lithium users.
Leads to DI and renal insufficiency.
Kidneys are normal to small volume, multiple tiny cysts, usually 2-5mm.
These are distinguishable from larger cysts associated with acquired uraemia.
Multicystic dysplastic kidney (3)
Kids, multiple tiny cysts forming in utero.
No functioning renal tissue.
Contralateral renal tract abnormalities occur 50% of the time
