Congenital Anomalies of the Kidneys and Urinary Tract

Unilateral Renal Agenesis

• Unilateral renal agenesis (URA) is defined as the one-sided congenital absence of renal tissue resulting from failure of embryonic kidney formation. Human renal development is characterized by highly orchestrated interactions between the outgrowing ureteric bud of the mesonephric duct and the metanephric blastema. As a consequence, renal agenesis occurs when the ureteric bud fails to form the ureter, the renal pelvis, the collecting ducts  and the renal mesenchyme to form nephrons. Unilateral renal agenesis occurs with incidence of one in 500 to 1000 births. It has autosomal dominant type of inheritance. The bladder trigone normally develops by absorption of the ureteric bud into the urogenital sinus. When the ureteric bud fails to form the ureter, it also fails to form the bladder trigone on one side. Hence there is absence of ureter and ipsilateral absence of hemi-trigone. Ipsilateral testes and vas deferens are also absent. Adrenal gland is usually present.

Bilateral Kidney Agenesis

Bilateral kidney agenesis is the absence of both kidneys at birth. It is a genetic disorder characterized by a failure of the kidneys to develop in a fetus. This absence of kidneys causes a deficiency of amniotic fluid (Oligohydramnios) in a pregnant woman. Normally, the amniotic fluid acts as a cushion for the developing fetus. When there is an insufficient amount of this fluid, compression of the fetus may occur resulting in further malformations of the baby like Potters syndrome.

Potters Syndrome

• POTTERS FACIES- Low set ears, beaked nose, prominent epicanthic folds and downward slant of eyes, pulmonary hypoplasia causing respiratory failure and limb deformities. Bilateral renal agenesis is incompatible with life.

Multicystic Disease

• A Multicystic Dysplastic Kidney (MCDK) is the result of abnormal fetal development of the kidney (congenital anomaly of kidney). The kidney consists of irregular cysts of varying sizes. This congenital severe renal dysplasia, condition with mass of various sized cysts in the loose stroma occurs with an incidence of  one in 4500 births. The newborn child presents with the palpable mass in the abdomen.  The multicystic disease is always associated with atresia of ipsilateral ureter. Treatment: in asymptomatic patients observation is necessary. If the patient develops recurrent infections or pain or recurrent fever or if the patient develops hypertension then nephrectomy is done. Sometimes the contralateral kidney may develop PUJ (pelviureteric junction) obstruction or can present with hydronephrosis.

Crossed Fused Ectopia

The kidney crosses the midline and goes to the opposite side, but the ureters open at the normal position.

Horse Shoe Kidney

• Horseshoe kidney is one of the congenital anomaly of kidney in which the both lower poles of the kidneys are fused in 95% of the cases. The inferior mesenteric artery prevents the normal upward ascent of the kidneys from the pelvis and therefore kidneys are situated at a lower level. The congenital anomaly occurs with an incidence of one in 1000 births and more common in males than in females (2:1).

Clinical Features

• In most of the patients there are no symptoms. Rarely patients may present with urinary tract infection, pelvi ureteric junction obstruction, reflex disease.

Diagnosis

• Intravenous pyelogram may reveal shake hand sign and flower vase bend sign of the ureter. A patient with horse show kidney has an increased risk of developing Wilms tumour, renal carcinoid and upper urinary tract transitional cell carcinoma. The most common tumour in horseshoe kidney is renal cell carcinoma. During the surgery, isthmus is never cut because of the overlapping blood supply the lower pole may become ischaemic.

Duplication Of Ureter

• A duplicated ureter occurs when two ureters form on the same kidney. One ureter drains from the upper pole and the other ureter drains from the lower pole of the kidney. Duplication of the ureter occurs with an incidence of 1 in 150 births. It is more common on the left side than on the right and more common in females than in males.

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Duplication Of Ureter Is Of 2 Types

1. Incomplete Duplex Ureter
   • In this condition 2 ureters draining from upper and lower pole separately fuses to form a single ureter and opens as single opening on the urinary bladder. This condition occurs because during the development a single ureteric bud arises but bifurcates before meeting the metanephric blastema.
2. Complete Duplex Ureter
   • In this condition 2 ureters draining from the upper and lower pole of the kidney separately opens on to the urinary bladder with 2 openings. This condition arises due to the development of 2 separate ureteric buds during the development.            

• WEIGHERT MEYER RULE: The ureter draining from the upper pole opens caudally, medially and at ectopic location on the urinary bladder and it is frequently associated with obstruction. The ureter draining from the lower pole opens cranially, laterally on the urinary bladder and it is associated with reflux.

Diagnosis

• On intravenous pyelogram drooping water lilly sign  is visualised due to the duplication of ureter with non functioning upper pole of the kidney.

Opening Of Ectopic Ureter

• In males, the most common site of opening of ectopic ureter is at prostatic urethra. The other sites include -seminal vesicle, neck of the bladder, epididymis. In males, the ectopic ureter always opens proximal to the external urethral sphincter. So in males incontinence never occurs. The clinical presentation is urinary tract infections in males. In females the most common site of ectopic ureter is distal urethra or vagina. The opening is distal to the urethral sphincter so the presenting feature in females is incontinence of urine. Continuous dribbling of urine along with normal voiding is the clinical feature that is seen in females.

Treatment

• Ectopic ureter with obstruction and upper pole of the kidney are nonfunctioning, then partial nephrectomy is done. When there is normal renal function then ureteric reimplantation is done.

Ureterocoel

• Ureterocele is congenital condition in which there is cystic enlargement of the intramural part of the ureter. It is a developmental anomaly due to atresia of the ureteric orifice. Ureterocele is more common in females than in males. Ureterocele is bilateral in 10% of the cases. On radiological examination, ureterocele appears as adder head appearance or cobra head appearance. On voiding cystourethrogram ureterocele appears as translucent filling defect of the bladder. On cystoscopy it appears as narrowed and bulged orifice.

Treatment Of Ureterocele

• Simple ureterocele-the treatment is surgical excision with reimplantation of the ureter or endoscopic incision or smiley incision can be done. This may result in reflex. In advanced unilateral cases with hydronephrosis or pyonephrosis, nephrectomy is indicated.

Retrocaval Ureter

• Retrocaval ureter (RCU) is a rare congenital anomaly in which the ureter passes posterior to the inferior vena cava (IVC). This leads to the obstruction of the ureter and hydronephrosis of the kidney. On radiological examination fish hook ureter or reverse J shaped ureter sign appearance is seen.

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Polycystic Kidney Disease

• Polycystic kidney disease is divided into 2 types autosomal dominant polycystic kidney disease and autosomal recessive polycystic kidney disease

Autosomal Recessive Polycystic Kidney Disease

• This occurs due to defect in chromosome 6p21 (fibrocystin/polyductin). This congenital anomaly of kidney manifests in infancy, with reduced intrauterine urine secretion leading to oligohydramnios, Potter facies, and pulmonary hypoplasia.  There is hepatic involvement occurring in all the cases of autosomal recessive polycystic kidney disease (Congenital hepatic fibrosis, biliary ectasia and Peri portal fibrosis) occurs. On ultrasonography homogeneously hyper echogenic kidney is noted. This condition has poor prognosis, usually the child dies in the intrauterine or within first 2 months of birth.

Autosomal Dominant Polycystic Kidney Disease

• It is the most common inheritable cystic diseases. ADPKD-1 gene is present on chromosome 16 and produces polycystin1 protein. ADPKD-2 gene is present on the chromosome 4 producers polycystin 2 protein. These proteins play a critical role in normal functioning of the primary cilium. They are essential for maintaining the differential phenotype of tubular epithelium. The ballooning of the tubular epithelium takes place with the mutations leading to the formation of the cysts. It has an incidence of one in 400 to 1000 births.

Diagnostic Criteria On Ultrasonography

• Atleast 3 (unilateral/ bilateral ) renal cysts and 2 cysts in each kidney are sufficient for diagnosing at risk individuals aged 15-39years.

Clinical Features

• Most common feature in autosomal dominant polycystic kidney disease is pain ( pain occurs due to the distension of the capsule). Most common presenting feature is hypertension.

(after the age of 20years, most of the patients develop hypertension.)

Renal Manifestations

• Renal enlargement which is manifested as abdominal lump.  Dull loin pain due to distention of the capsule.  Any acute severe pain maybe due to the hemorrhage in the cyst of the kidney. 40% of the patients have visible hematuria. Urinary tract infections and sterile pyuria. Nephrolithiasis is present in 20% of the patients with autosomal dominant polycystic kidney disease, which are mostly uric acid or calcium oxalate crystals or both.

Diagnosis

• On intravenous pyelogram spider leg appearance is seen.  The renal pelvis is thinned out due to the presence of the cysts which appears on the radiograph like a spider leg.

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Extra Renal Manifestations Of Adult Polycystic Kidney Disease

• Multiple cysts in the liver, spleen, and pancreas, berry aneurysm in 10% of the patients, mitral valve prolapse in 25% of the patients, colonic diverticula. Most common extra renal manifestation is cyst in liver. The most common cause of death in patients with autosomal dominant polycystic kidney disease is chronic renal failure. Chronic renal failure tends to occur in males at younger age than in females. Vasopressin antagonist, somatostatin analogue, mTOR inhibitors prevent the cytogenesis, cyst expansion and declining renal function.

Anomalies Of Renal Vasculature

• Renal vasculature anomalies are more common on the left side than on the right side. Arterial anomalies are more common than venous anomalies. The most common vascular anomaly overall is supernumerary renal artery. The most common venous anomaly on right side is accessory renal vein and on left side is circumflex aortic renal vein.

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