Polycystic kidney disease (PKD) is a hereditary disorder with an unclear pathogenesis. It may be associated with tubule obstruction or localized dilation in different sections of the nephron. The disease typically affects both kidneys, beginning with a few cysts in the renal parenchyma and progressively evolving into a condition where the entire kidney is covered with numerous cysts of varying sizes. These cysts exert pressure on the renal parenchyma, reducing the number of functioning nephrons. Polycystic kidney disease is classified into an infantile type and an adult type.
Infantile Polycystic Kidney Disease (ARPKD)
This form is inherited in an autosomal recessive pattern and involves mutations in the PKHD1 gene on chromosome 6. It is commonly associated with cysts in the liver, spleen, or pancreas. Its incidence is approximately 1 in 10,000. Renal or hepatic insufficiency often occurs in childhood, and early death is common.
Adult Polycystic Kidney Disease (ADPKD)
This form follows an autosomal dominant inheritance pattern and has an incidence of approximately 1 in 1,250, accounting for roughly 10% of end-stage kidney disease cases. Among the children of affected adults, 50% inherit the disease. The PKD1 gene is located on the short arm of chromosome 16 and accounts for 85%–90% of cases, while the PKD2 gene is situated on chromosome 4 and accounts for 5%–10% of cases. In some patients, mutations in PKD1 and PKD2 are absent, suggesting the existence of a PKD3 gene. Clinical manifestations of PKD1 and PKD2 mutations are similar; however, PKD2 mutations are associated with a later onset and slower disease progression. Most cases of ADPKD manifest symptoms around 40 years of age, and the main clinical features include pain, abdominal masses, and impaired renal function. If accompanied by kidney stones or urinary tract infections, additional symptoms such as hematuria, pyuria, fever, and flank pain may present. Approximately one-third of affected patients have concurrent polycystic liver disease, which typically does not affect liver function. Complications include uremia, hypertension, myocardial infarction, and intracranial hemorrhage. Physical examination frequently reveals large cystic kidneys in both flanks, and diagnostic confirmation can be achieved through ultrasound and CT imaging.
Polycystic kidney disease should be differentiated from multiple simple renal cysts. PKD is often hereditary, with other family members being affected, and is typically accompanied by reduced renal function and polycystic liver disease. In contrast, simple renal cysts are more common and are mostly nonhereditary. Early-stage simple cysts typically do not cause obvious symptoms and are often discovered incidentally. They may present with flank or back pain and microscopic hematuria. Simple cysts are usually singular but may also be multiple or bilateral. Ultrasound and CT imaging are helpful for differentiation.
For patients with normal renal function, symptomatic and supportive treatment is recommended, including rest, a low-protein diet, and avoidance of physical strain. Drug treatments focus on managing blood pressure, preventing urinary tract infections, and mitigating further renal impairment. Patients with stone-related obstructions may undergo lithotomy to relieve the obstruction. The efficacy of cyst decortication in lowering blood pressure, reducing pain, and improving renal function remains controversial. At advanced stages, when uremia arises, long-term dialysis or renal transplantation becomes necessary. For patients with severe hypertension, bleeding, or infections, nephrectomy prior to transplantation may be considered.