Polycystic kidney disease

What is polycystic kidney disease?

Polycystic kidney disease (PKD) is a genetic disorder characterised by the growth of numerous cysts in the kidneys. The cysts are filled with fluid. PKD cysts can slowly replace much of the mass of the kidneys, reducing kidney function and leading to kidney failure.

What are the causes?

Polycystic kidney disease (PKD) is an inherited disorder (with autosomal dominant inheritance). If one parent carries the gene, 50% of the children will develop the disorder. The exact mechanism that triggers cyst formation is unknown. Cysts in the kidneys may be associated with aneurysms of the blood vessels in the brain. They may be associated with diverticula of the colon, and with cysts in the liver, pancreas, and testes. As many as 50% of people with polycystic kidney disease also have cysts in the liver.

What are the types?

Autosomal dominant PKD (ADPKD) is the most common, inherited form. Symptoms usually develop between the ages of 30 and 40, but they can begin earlier, even in childhood. About 90 percent of all PKD cases are autosomal dominant PKD.

Autosomal recessive PKD is a rare, inherited form. Symptoms of autosomal recessive PKD begin in the earliest months of life, even in the womb.

Acquired cystic kidney disease (ACKD) develops in association with long-term kidney problems, especially in patients who have kidney failure and who have been on dialysis for a long time. Therefore, it tends to occur in later years of life. It is not an inherited form of PKD.

What are the symptoms?

In early stages of the disease, the cysts enlarge the kidney and interfere with kidney function, resulting in chronic high blood pressure, anaemia, and kidney infections. The cysts may cause the kidneys to increase production of erythropoietin (the hormone that stimulates production of red blood cells) resulting in increased number of red blood cells, rather than the expected anaemia. Hypertension caused by polycystic kidneys may be difficult to control. The disease is slowly progressive, eventually resulting in end-stage kidney failure. It is also associated with liver disease, including infection of liver cysts. The presenting symptoms include:

• blood in the urine
  
• flank pain on one or both sides
  
• excessive urination at night
  
• abdominal pain or tenderness

Additional symptoms that may be associated with this disease:

• nail abnormalities
  
• painful menstruation
  
• joint pain
  
• drowsiness
  
• high blood pressure

How is it diagnosed?

Examination may show high blood pressure, kidneys or abdominal masses which are felt during examination, abdominal tenderness over the liver (right upper quadrant), and enlarged liver.

• A urinalysis is nonspecific, but it may show urine protein or blood in the urine.
  
• A CBC (complete blood count) may show decreased or increased RBCs

Polycystic kidney disease, and associated cysts on the liver or other organs, may show on:

• abdominal ultrasound
  
• abdominal CT scan
  
• abdominal MRI scan

In a family with several affected members, genetic linkage tests can be performed to determine with fair reliability whether a person at risk carries the gene for ADPKD.

What is the treatment?

Currently, no treatment can prevent the cysts from forming or enlarging. Treatment aims at reducing the symptoms and prevention of complications.

-Medicine and surgery to reduce pain

-Antibiotics to resolve infections

-Dialysis and transplantation to replace functions of failed kidneys

Hypertension may be difficult to control, but control of it is the most important aspect of treatment. Treatment may include antihypertensive and/or diuretic medications, low salt diet, or other treatments. A urinary infection should be treated promptly with appropriate antibiotics. If there are symptoms of anaemia, it may be treated with iron and other supplements, erythropoietin administration, or blood transfusion.

Surgical or radiologic drainage of cysts may be indicated because of pain, bleeding, infection, or obstruction. There are usually too many cysts to make cyst removal a feasible alternative. Surgical removal of one or both kidneys may be required. Treatment of end-stage kidney disease includes kidney or kidney transplantation.

What is the prognosis?

Medical treatment may provide relief of symptoms for many years. More importantly, strict control of blood pressure and avoidance of exposure to potential kidney toxic medications helps to delay the progression of kidney disease process over period of years.

Patients with kidney failure from polycystic kidney disease who get kidney transplantation do have good outcome.