Polycystic kidney disease (PKD) may be autosomal dominant or autosomal recessive, depending on the genetic pattern. The complications are similar in many respects, but the time of onset, the severity and the associated risks are different.
The complications of autosomal dominant PKD include:
Most patients with AKPKD complain of pain at some point, and it is often the presenting symptom. Possible causes of acute pain may be a hemorrhage into a cyst or renal calculi with or without obstruction.Chronic pain occurse more often due to cyst infection, urinary tract infections or cyst growth causing stretching of the renal capsule.
Fever may present in some patients due to acute infection (acute pyelonephritis) or retroperitoneal rupture of a cyst.
While hypertension complicates ADPKD in approximately half the cases at initial presentation, kidney function is usually clinically normal at this stage. However, once renal insufficiency and failure sets in, almost all patients develop severe hypertension. This may be marked by symptoms such as dizziness, vomiting, dyspnea, diplopia and headache. The risks of high blood pressure include:
- Aggravation of renal damage
- Shorter time to onset of renal failure
- Heart disease
- Cerebrovascular accidents
Early occurrence of renal insufficiency may also occur due to:
- abnormal renal architecture
- inefficient countercurrent multiplication
- poor solute and ammonia sequestration in the renal medulla
The frequency of urinary tract infections is increased because of several factors, such as:
- Stagnation of urine due to obstruction of urinary flow by the cysts
- Infection of the renal cysts themselves
Complications of frequent UTIs include permanent fibrosis and further deterioration of renal function.
Renal calculi occur in 2 of every 10 people with ADPKD. The increased frequency of urate and oxalate stones may be due to reduced ammonia secretion in urine, increased protein intake, low urinary pH or low levels of urinary citrate. These can cause symptoms such as:
- Severe colicky pain in the lower back, loin or groin region
- Nausea, vomiting or diarrhea
- Fever with chills and rigor
- Inability to lie still in one position
Renal failure occurs when there is no longer sufficient intact renal tissue to support normal function. People with ADPKD go into renal failure around the age of 70 years, on average. End-stage renal disease is more common in males with ADPKD, for unknown causes.
The reasons for renal failure include:
- Destruction of the normal nephrons by expanding cysts
- Sclerosis of the renal arterioles and capillaries
- Interstitial inflammation and consequent fibrosis
- Death of the renal tubular epithelium by apoptosis
An individual may notice the following symptoms:
- Edema of the dependent parts of the body, such as around the ankles or feet, or around the eyes on waking from sleep
- Lowered urine output
- Feeling of malaise
- Dry skin
- Respiratory difficulty
Liver cysts are extremely common in ADPKD, but are generally asymptomatic.
Pancreatic cysts may also occur in AKPKD, and may result in pancreatitis.
Heart valve abnormalities are found in up to a fourth of people with ADPKD, including mitral valve prolapse, aortic root insufficiency and aortic dissection. Symptoms of these may range from none to severely limited exercise tolerance with aortic root dilatation, to chest pain and back pain with dissection of the thoracic aorta.
Colonic diverticula may lead to colicky pain in the abdomen, characteristically left-sided, with bloating, or alterations in the passage of feces. At this stage the patient usually has end-stage renal disease. However, in most patients the condition is asymptomatic, though it may be complicated by hemorrhage into or infection of the diverticula.
Aneurysms, most often in the brain, but also in the aorta or the coronary vessels. A brain aneurysm may occur in only 4% of young patients, but up to a tenth of older patients. It may present with severe headaches, often with forceful vomiting and Cerebrovascular bleeding following aneurysm rupture, which usually happens by age 50 in up to 75% of such individuals. The risk of rupture is high if the following factors are present:
- Hypertension which is not under control
- Family history of aneurysms or of rupture
- Large aneurysms
Complications of ARPKD
In the recessive form, polycystic kidney disease is far more severe and renal failure occurs early. The complications may be present at birth, and include:
Severe respiratory failure, due to pulmonary hypoplasia. This is because of abnormal pressure on the lungs by the enlarged kidneys, during intrauterine life. Simultaneously, pressure continuing after birth makes lung inflation difficult. 30% of these infants die within a year because of pulmonary complications, which include:
- Respiratory insufficiency
- The need for mechanical ventilation
- Frequent lung infections
Failure to thrive, which may be due to several factors such as:
- Poor appetite
- Limited gastric capacity due to the enlargement of the kidneys
- Vomiting after a feed
- Progression to chronic kidney disease
- Lack of normal renal function
- Hepatic dysfunction
- Repeated infections of the kidneys and the liver
Renal failure in childhood, usually before the age of 20, which requires renal replacement therapy or a kidney transplant. Liver cirrhosis as a result of the development of multiple liver cysts, leading to:
- progressive portal hypertension in up to 70%
- liver enlargement due to dilatation of the intrahepatic biliary ducts, in 30-60% of children at first presentation
- ascending cholangitis
- hepatic dysfunction
- internal varices
- Internal bleeding from ruptured varices which develop as a result of portal hypertension
Some patients may also be affected by hypertension, which further aggravates renal damage and frequent urinary tract infections.
Reviewed by Yolanda Smith, BPharm