The importance of inheritance and the familial incidence of disease warrant the inclusion of a classification of hereditary renal diseases. Although relatively uncommon in the population at large, hereditary renal disease must be recognized to permit early diagnosis for detection and genetic counseling.
Chronic Hereditary Nephritis
Evidence of the disease usually appears in childhood, with episodes of hematuria. Renal insufficiency commonly develops in males but only rarely in females. Survival beyond age 40 is rare.
In many families, deafness and abnormalities of the eyes accompany the renal disease (so-called Alport disease). Another form of the disease is accompanied by polyneuropathy. Infection of the urinary tract is a common complication.
There is splitting and thickening of the GBM or podocyte proliferation and thickening of Bowman’s capsule. Recently, kindreds have been described that have “thin-membrane disease.” This condition is characterized by microscopic hematuria and, often, later progression to chronic renal failure. This, like Alport disease, may represent inherited abnormalities or deficiencies in type IV collagen in the GBM. This affects both genders.
Laboratory findings with these conditions are commensurate with existing renal function. Treatment is symptomatic.
Cystic Diseases of the Kidney
Congenital structural anomalies of the kidney must be considered in any patient with hypertension, pyelonephritis, or renal insufficiency. Many of these patients are at increased risk of urinary tract infection.
A. Polycyctic Kidneys
Polycystic kidney disease is familial and often involves not only the kidney but the liver and pancreas as well. It is clear that at least 2 genetic loci can lead to autosomal dominant polycystic kidney disease.
The formation of cysts on the cortex of the kidney is thought to result from failure of union of the collecting tubules and convoluted tubules of some nephrons. Intrarenal cysts may be of a proximal or a distal luminal type, differing on analysis by their cyst electrolyte content. This is important if one or more of these cysts become infected, and an antibiotic (with varying cyst-type penetrance) is chosen. New cysts do not form, but those present enlarge and, by exerting pressure, cause destruction of adjacent renal tissue. The incidence of cerebral vessel aneurysms and cardiac valve prolapse is higher than normal.
Cases of polycystic disease are discovered during the investigation of hypertension, by diagnostic study in patients presenting with pyelonephritis or hematuria, or by investigation of families of patients with known polycystic disease. At times, flank pain due to hemorrhage into a cyst occurs. Otherwise the symptoms and signs are those commonly seen in hypertension or renal insufficiency. On physical examination, the enlarged, irregular kidneys are often easily palpable.
The urine may contain leukocytes and erythrocytes.
With bleeding into the cysts, there may also be bleeding into the urinary tract. The blood chemistry findings reflect the degree of renal insufficiency. Examination by sonography, CT scan, or x-ray shows the enlarged kidneys, and urography demonstrates the classic elongated calyces and renal pelves stretched over the surface of the cysts.
No specific therapy is available, and surgical interference is only indicated to decompress very large cysts in patients with severe pain.
Patients with polycystic kidney disease live in reasonable comfort with slowly advancing uremia. Both hemodialysis and renal transplantation extend the life of these patients. Nephrectomy is indicated only in patients with recurrent infections, severe recurrent bleeding, or markedly enlarged kidneys.
B. Cystic Disease of the Renal Medulla
1. Medullary cystic disease–
Medullary cystic disease is a familial disease that may become symptomatic during adolescence. Anemia is usually the initial manifestation, but azotemia, acidosis, and hyperphosphatemia soon become evident. Urine findings are not remarkable, although there is often an inability to concentrate and renal salt wasting often occurs. Many small cysts are scattered through the renal medulla. Renal transplantation is indicated by the usual criteria.
2. Medullary sponge kidney–
Medullary sponge kidney is asymptomatic and is discovered by the characteristic appearance of tubular ectasia in the urogram. Enlargement of the papillae and calyces and small cavities within the pyramids is demonstrated by the contrast media in the excretory urogram. Many small calculi often occupy the cysts, and infection may be troublesome. Life expectancy is not affected and only therapy for ureteral stone or for infection is required.