Genitourinary Tract, GUT

Genitourinary Tract, GUT


INTRODUCTION


Anatomy


  Left kidney usually lies—1–2 centimeters higher than the right. Extends from T12-L3 vertebrae usually.


  Normal kidney measures approximately 9–13 centimeters in length and 4–6 centimeters in width. Size of both the kidneys should not differ by >2 centimeters (Figure 7.1).


  Renal parenchyma is composed of


Cortex: Usually less echogenic than the adjacent liver and spleen.


Medullary pyramids: More hypoechoic than cortex.


  Echogenic renal sinus containing urine collecting system, blood vessels, fat, and fibrous tissue seen in the center of kidney.


  The kidney has a thin, fibrous true capsule. Perirenal fat lies outside this capsule, encased anteriorly by the fascia of Gerota and posteriorly by the fascia of Zuckerandl.


Vascular anatomy


Bilateral renal arteries arise from aorta at L1-2 vertebral body level.


Left renal vein is longer, passes between aorta and superior mesenteric artery (SMA) before entering into IVC.


Left gonadal vein drains into the left renal vein.


Right renal artery is longer, courses inferiorly, and passes posterior to IVC and right renal vein.


Image


Figure 7.1 Depicting normal echotexture of right kidney in comparison to liver.


Left renal artery passes posterior to the left renal vein.


Four protective layers covering the kidney (inner to outer):


1.    Fibrous capsule


2.    Perirenal fat


3.    Gerota’s fascia


4.    Pararenal fat


Ureters


30–34 centimeters long and 2–8 millimeters diameter. Nondilated ureter may not be visualized due to the overlying bowel gas. Normally, lie anterior to iliac vessels.


Bladder


Trigone is an area demarcated by the ureteric and urethral orifices within the bladder. The wall thickness of bladder depends on the degree of bladder distension. Should be moderately filled for proper visualization. Normal bladder capacity is ~400–500 milliliters. Postvoid scan should be done to rule out any lower urinary tract pathology.


Normal variants


Hypertrophied column of Bertin: Normal variant representing the unresorbed polar parenchyma.


Sonographically, usually, seen at the junction of upper and middle thirds of the kidney.


Bordered by junctional parenchymal defect.


Indentation of renal sinus laterally.


Continuous with adjacent renal cortex.


It contains renal pyramids.


Generally <3 centimeters. May be misinterpreted for a small tumor. Presence of arcuate arteries by color Doppler (CD) differentiates it from a small tumor.


Renal hypoplasia: Kidney is small in size but otherwise normal.


Persistent fetal lobulation: Fetal kidney is normally lobulated. May persist as normal variant in adults.


Dromedary hump: Normal variant of contour of kidney due to splenic impression into superolateral border of the left kidney. It may simulate a renal mass but calyces and pyramids may extend into this pseudotumor.


PATHOLOGIES


Hydronephrosis


Dilated calyceal system and continuity of calyceal with renal pelvis differentiates it from cysts. Pelvi–calyceal system may dilate due to overhydration, overfilled urinary bladder (relieves after micturition), and pregnancy.


Grade1: Minimal splitting of pelvis—may be due to overfilled bladder.


Grade2: Mild—dilated pelvis and calyces.


Grade3: Moderate—both pelvis and calyceal system are dilated with mild parenchymal atrophy.


Grade4: Severe—markedly dilated pelvi–calyceal system with severe thinning of renal parenchyma (Figure 7.2).


Image


Figure 7.2 Depicting varying grades of hydronephrosis as mild as moderate and severe.


Congenital anomalies


RENAL DUPLICATION


Partial or complete duplication of the collecting system.


WEIGERT–MEYER RULE


The lower pole collecting system inserts into the bladder at the normal site, but intramural portion may be shorter than usual leading to vesicoureteric reflux (VUR).


The upper pole ureter inserts ectopically inferomedial to the site of normal ureteral insertion. Its orifice may be stenosed and obstructed.


Patients with complicated renal duplications may present with urinary tract infections, failure to thrive, hematuria, and symptoms of bladder obstruction.


Females with urethral insertion of the upper pole ureter below the external urinary sphincter may present with chronic constant urinary incontinence or dribbling.


ECTOPIC KIDNEY


Failure of kidney to ascend during embryologic development results in pelvic kidney.


Kidneys are small sized with reduced functioning.


Ureters are short (Figure 7.3).


If the kidney ascends too high, it passes through Bochdalek’s foramen, results in thoracic kidney.


Image


Figure 7.3 Showing ectopic right kidney in the pelvis.


Image


Figure 7.4 Illustrating normal right kidney cross fused with ectopic right kidney.


CROSSED FUSED ECTOPIA


Both kidneys are found on the same side.


Ectopic kidney will be fused to the other kidney (Figure 7.4).


Ureteric-vesical junction (UVJ) is normally located.


HORSESHOE KIDNEY


Lies anterior to the abdominal great vessels.


Fusion of lower poles with either functioning or fibrous isthmus.


Associated with pelvi-ureteric junction (PUJ) obstruction, VUR, and so on.


On sonography, kidneys are lower than normal with the poles projecting medially (Figure 7.5).


Hydronephrosis and calculi may be seen.


Image


Figure 7.5 Illustrating horseshoe kidney.


Image


Figure 7.6 Illustrating PUJ obstruction.


PELVI-URETERIC JUNCTION OBSTRUCTION


M:F=2:1.


Left > Right.


On sonography, hydronephrosis up to the level of pelvi-ureteric junction.


Marked ballooning of the renal pelvis is present (Figure 7.6).


Infective lesions


ACUTE PYELONEPHRITIS


Usually kidneys appear normal. If abnormal, may show


  Altered echotexture


  Renal enlargement


  Loss of cortico-medullary differentiation


If focal, may appear as hypoechoic masses.


Untreated or inadequately treated APN may lead to parenchymal necrosis with abscess formation.


Diabetics, immunocompromised, and patients with chronic debilitating diseases are at an increased risk.


On USG, round, thick-walled hypoechoic complex masses with internal mobile debris.


Sometimes gas with dirty shadowing may also be seen.


D/D


  Hemorrhagic/infected cysts


  Parasitic cysts


  Multilocular cysts/cystic neoplasms


Small abscess: Treated conservatively.


Large abscess: Requires per cutaneous drainage/surgery.


PYONEPHROSIS


Purulent material in an obstructed collecting system


On sonography, hydronephrosis ± hydroureter


  Mobile debris (Figure 7.7)


  Gas with dirty shadowing may be seen


  Stones may be seen


CHRONIC PYELONEPHRITIS


Interstitial nephritis often associated with VUR.


On sonography


  Echogenic parenchyma with atrophy


  Dilated collecting system


Image


Figure 7.7 Depicting dilatation of pelvicalyceal system and ureter with enlarged kidney and echogenic debris suggesting pyoureteronephrosis.


Image


Figure 7.8 Depicting thickened and irregular bladder wall in a patient with cystitis.


CYSTITIS


Usually caused by E. coli.


Presents with bladder irritability and hematuria.


On sonography


  Diffuse irregular bladder wall thickening (Figure 7.8)


  Internal mobile echoes in the lumen may be seen


Calculi


RENAL CALCULI


Most common type of stone is calcium oxalate (60%–80%).


Three areas of ureteric narrowing where the stone may lodge:


1.    Just past the PUJ


2.    Where the ureter crosses the iliac vessels


3.    At the UVJ (most common site as ureter has its smallest diameter of 1–5 millimeters here)


On sonography → echogenic foci with distal acoustic shadowing seen and proximal hydroureteronephrosis. Sometimes hydronephrosis may not be present suggesting nonobstructing calculi. Twinkling artifacts may be seen on Doppler.


Staghorn calculus—coral calculus—take the shape of renal pelvis resembling horns of a stag. Occur due to recurrent infection; usually composed of struvite (Magnesium, Ammonium, Phosphate [MAP]).


Entities that mimic renal calculi


  Renal artery calcifications


  Intrarenal gas


  Calcified sloughed papilla


Image


Figure 7.9 Showing a calculus at VUJ leading to upstream hydroureteronephrosis.

Nov 6, 2018 | Posted by in ULTRASONOGRAPHY | Comments Off on Genitourinary Tract, GUT
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