Diagnosis of Polycystic Kidney Disease

Progression of Autosomal Dominant Polycystic Kidney Disease

A patient's physical condition can be normal for many years after cysts start forming and physical checkups and blood tests may not show any additional signs of the autosomal dominant polycystic kidney disease (ADPKD). As the disease progresses, the kidneys gradually increase in size in addition to losing the ability to remove wastes and toxins from the blood, including creatinine. Since the buildup of toxins leads to uremia or "uremic poisoning" and precedes "end-stage renal disease" (ESRD), dialysis or renal transplantation is necessary to take over the functions of the kidneys. Renal failure usually develops between 40 and 60 years of age in ADPKD patients.

In general, the number and severity of symptoms and complications tend to increase with age. These include:

  • Hypertension
  • Pain
  • Extrarenal cysts (cysts outside the kidney)
  • Intracranial aneurysms
  • Circulatory disturbances
  • Diverticular disease

Hypertension

Hypertension (high blood pressure) is closely associated with ADPKD and develops in approximately 70% of adults and 10-15% of children before the onset of renal failure. It is often one of the earliest symptoms of PKD. A relationship appears to exist between the volume of the kidneys and the severity of hypertension.

It is thought that the rise in blood pressure may be secondary to renal damage caused by the cysts. Renal ischemia, the obstruction of the blood vessels due to compression by the cysts and resulting increased mass of the kidney, results in reduced blood flow and reduced delivery of oxygen to the kidney. This increases the release of renin and results in elevated blood pressure.

Hypertension ultimately contributes to elevating cardiovascular risk and to progression of renal failure.

Pain

Pain is one of the most common symptoms in polycystic kidney disease and is found in about half of PKD patients. Pain can be due to several causes, can be acute or chronic, and can range from mild to very severe. Imaging using computerized tomography (CT), magnetic resonance imaging (MRI), or ultrasound is most effective in pinpointing which cysts are largest or which may be the source of greatest pain.

The pain may be felt in the region of the kidneys (back, sides, and under the ribs) as well as in the abdomen due to the pressure resulting from the enlarged kidneys.

Acute Pain

Acute pain can be due many factors including:

  • Infection - this may be due to a urinary tract infection or infection of the cysts.

  • Hematuria - Gross hematuria (blood that is visible in the urine) occurs in approximately 50% of patients with PKD and is associated with rupture of renal cysts. This occurs when cysts rupture and hemorrhage into the urinary tract. It is associated with flank pain (pain between the upper abdomen and the back). Increased frequency of episodes of gross hematuria may indicate a worse prognosis. Episodes of hematuria usually last from 2-7 days and usually resolve with bedrest and hydration.

  • Kidney Stones - Kidney stones (nephrolithiasis) occur in up to 30% of people with PKD and can cause considerable pain, usually in the flank. Impaired drainage of the kidney because of PKD may lead to crystal formation that may accumulate and develop into stones. Kidney stones are also associated with urinary tract infections and hematuria. Renal function in patients with polycystic kidney disease who develop kidney stones is usually worse than in PKD patients without stones. Some researchers correlate the development of kidney stones with individuals who exhibit large numbers of cysts and for whom cyst size is large.

Chronic Pain

The source of chronic pain may include:

  • Cyst formation - Cyst formation causes increase in size and compression of the kidney and may be associated with constant, but not necessarily severe, pain which is worse when standing or walking. Cyst formation in the liver can be extensive and even more painful than in the kidneys.

  • Mechanical changes of the spine - The size and location of the cysts (kidney or liver) can cause changes in abdominal girth which impact posture and can be associated with spinal changes. When the abdomen enlarges, it places pressure on the lumbar spine which can cause changes on muscles supporting the spine which can cause significant pain.

Extrarenal Cysts

Extrarenal cysts are cysts that develop outside of the kidney. Approximately 60% of patients with PKD develop cysts in the liver which can be even more painful than kidney cysts. Women who have had multiple pregnancies seem to develop larger cysts and more cysts than men. Liver cysts can become quite massive, however, liver failure is rare. The incidence of liver cysts increases with age.

Cysts in the kidneys or liver can become so large that they compress the stomach and cause a feeling of satiety in the patient. These patients must be carefully monitored for unintentional weight loss.

Approximately 5% of patients develop cysts in the pancreas and approximately 3% of individuals with PKD develop cysts in the colon or spleen.

Intracranial Aneurysm

An intracranial aneurysm is a bulge or ballooning of the wall of a blood vessel in the brain. If the aneurysm ruptures, it can lead to the accumulation of blood in the brain and can cause massive brain swelling and even death. Intracranial aneurysms are a serious complication and occur in 4-10% of people with PKD. Rupture of an intracranial aneurysm usually occurs in patients under the age of 50 whose blood pressure is not well controlled.

Circulatory Disturbances

Circulatory disturbances in patients with PKD may include:

  • Anemia - underproduction of red blood cells
  • Cardiac hypertrophy - enlargement of the heart
  • Mitral valve prolapse - failure of the mitral valves in the heart to open and close properly which allows for a small amount of blood to flow back into the heart with each contraction (heartbeat). Mitral valve prolapse develops in approximately 25% of people with PKD.
  • Aortic aneurysm - a bulging or widening of the aorta (the large blood vessel that carries blood from the heart to the rest of the body).

Diverticular Disease

Diverticular disease refers to a range of conditions that develop from the presence of one or more small pouches (diverticula) that protrude from the wall of the large intestine (colon). Symptoms may include abdominal pain, constipation, diarrhea, and rectal bleeding. Diverticular disease occurs in up to 8% of patients with PKD.