Polycystic Kidney Disease
Introduction and Genetics:
This is one of the commonest genetic disorders affecting kidneys. The disease runs in families. The reported incidence is 1 in 400 to 1in 1000. Both man and woman are affected. If one parent is affected the children of the patient have 50% chance of inheriting the disease.
One-quarter of patients may not provide a history of the disease in parents or siblings because of death prior to diagnosis, an undiagnosed disease in the other members or insufficient investigation of the other family members.
The disease can be found by genetic testing in the fetus. However as the disease has normal mentation and causes problems in adult life, genetic testing in a fetus are rarely carried out.
The disease is usually of two types. 85% suffer from an abnormality of Chromosome 16 and rest from Chromosome no 4. Type PKD 1 (ch 16 variety) is the more severe form. It causes renal failure at about 55 Yrs of age while Type PKD II at 70 Yrs of age.
Those patients with hypertension, males, with larger kidney size develop renal failure early.
There are hundred to thousands of cysts distributed in both kidneys in all areas. Liver and pancreas, and sometimes lungs may also have cysts. A fewhave intracranial aneurysms( dilatation of blood vessels). Cardiac valvular defects are also common. Affected kidneys may have a stone formation or these can be infected.
Patients may have initial symptoms of abdominal pain due to large kidneys, high blood pressure or urinary tract infections. USG done for unrelated symptoms sometimes reveals the diagnosis.
In affected families, the no of cysts at various age groups helps in ascertaining the probability of disease. It has to be distinguished in initial cases (probands) where family history is not available, from other cystic diseases of the kidneys.
Treatment includes control of high blood pressure, statins, lower protein intake and general measures. Patients may waste salt in their urine and may suffer from low sodium levels. ACE inhibitors and ARBs are often used for the control of BP while care is taken to look for their side effects and safety.
A vasopressin inhibitor has been used increasingly for slowing/ Stopping the disease progression in ADPKD patients. It is more useful if started early before the s cr is very high.
Death is more often due to cardiac or strokes rather than kidney failure.