Congenital anomalies of The Kidney

1. agenesis --- kidneys don’t form (ureteric bud fails to develop)

2. hypoplasia --- could be unilateral or bilateral, failure of the kidney to form completely

3. ectopic kidney --- most of the time ends up in the pelvis, but there have been a few cases of ectopic kidneys found in the thorax (CPP)

4. horseshoe kidney --- there is a connection between upper or lower lobes of two kidneys, so it looks like a horshoe. 90% of horseshoe kidneys are fused at the lower poles.

5. Cysts: there are several categories, discussed below. This is usually a radiographic finding. Clinically, it is important to distinguish these from tumors.

   1. Adult Polycystic Kidney Disease: autosomal dominant, usually bilateral. Renal function is usually maintained until 3^rd or 4^th decade, when the patient presents with hematuria and hypertension (note, renal failure doesn’t occur right away). It is usually associated with other anomalies: hepatic cysts, mitral valve prolapse, berry aneurysms in circle of Willis.

   2. Infantile Polycystic Disease: autosomal recessive, usually bilateral, manifests with renal failure at birth or progresses to renal failure fairly quickly (contrast this with above). It is also associated with hepatic cysts, but not other abnormalities.

   3. Cystic renal dysplasia: associated with persistence of abnormal structures in the kidney, such as cartilage, undifferentiated mesenchyme. It could be unilateral or bilateral. It is usually associated with lower urinary tract obstruction (uretopelvic obstruction). That is, lower urinary tract obstruction could be causing cystic renal dysplasia, not the other way around. Kidney appears irregular and multisystic.

   4. Medullary Cystic Disease (2 different kinds)

---Medullary sponge kidney, where one has dilation of collecting tubules. Renal function is usually normal.

---Uremic medullary cystic disease, which is tubulo-intersitual in nature. This type of medually cystic disease can cause damage, i.e., progression to renal failure.

Patients on dialysis can also develop a cystic disease (obviously this type is not congenital).

The most common cyst in the kidney is called simple cyst. It is usually a post-mortem finding and usually doesn’t cause any problems. It needs to be distinguished from a tumor (tumor will appear more solid on ultra-sound)

Category: Nephrology Notes , Pathology Notes