Polycystic Kidney Disease (PKD)

Definition

Polycystic Kidney Disease (PKD) is a genetic disorder characterised by the growth of numerous cysts in the kidneys. These cysts are filled with fluid and can lead to enlarged kidneys and impaired kidney function over time. There are two main types: Autosomal Dominant PKD (ADPKD) and Autosomal Recessive PKD (ARPKD).

Aetiology

PKD is primarily caused by genetic mutations:

ADPKD: Caused by mutations in the PKD1 or PKD2 genes. It is inherited in an autosomal dominant pattern.
ARPKD: Caused by mutations in the PKHD1 gene. It is inherited in an autosomal recessive pattern.

Pathophysiology

In PKD, genetic mutations lead to the development of numerous fluid-filled cysts in the kidneys. These cysts can grow and multiply, causing the kidneys to enlarge and lose function over time. The cysts can also form in other organs, such as the liver, pancreas, and spleen. The progressive enlargement of the cysts disrupts normal kidney architecture, leading to hypertension, renal insufficiency, and eventually end-stage renal disease (ESRD).

Risk Factors

Family history of PKD
Genetic mutations in the PKD1, PKD2, or PKHD1 genes
Advanced maternal age (for ARPKD)

Signs and Symptoms

Symptoms of PKD can vary but often include:

High blood pressure (hypertension)
Back or side pain
Hematuria (blood in the urine)
Frequent urinary tract infections
Kidney stones
Enlarged abdomen due to enlarged kidneys
Kidney failure

Investigations

Clinical history and physical examination
Ultrasound: To detect cysts in the kidneys
CT scan or MRI: To provide detailed images of the kidneys and other organs
Genetic testing: To identify mutations in the PKD1, PKD2, or PKHD1 genes
Blood tests: To assess kidney function (e.g., serum creatinine, glomerular filtration rate)
Urinalysis: To detect blood or protein in the urine

Management

Primary Care Management

Blood pressure control: Using antihypertensive medications to manage hypertension
Pain management: Analgesics for back or side pain
Education: Informing patients about lifestyle modifications such as low-sodium diet and regular exercise
Monitoring: Regular follow-up to monitor kidney function and detect complications early
Referral: To a nephrologist for specialised care and further management

Specialist Management

Tolvaptan: A vasopressin V2 receptor antagonist that can slow the progression of ADPKD
Management of complications: Treatment for urinary tract infections, kidney stones, and cyst infections
Dialysis or kidney transplant: For patients with end-stage renal disease (ESRD)
Genetic counselling: For patients and families to understand the genetic nature of the disease and implications for relatives
Regular imaging: To monitor cyst growth and kidney function

Example Management for PKD

A patient diagnosed with ADPKD presenting with hypertension and back pain should have regular monitoring of blood pressure and kidney function. Management may include antihypertensive medications such as ACE inhibitors or angiotensin II receptor blockers (ARBs) for blood pressure control, and analgesics for pain management. Referral to a nephrologist is recommended for further evaluation and consideration of treatments such as Tolvaptan to slow disease progression. Lifestyle modifications, including a low-sodium diet and regular exercise, should be encouraged. Regular follow-up is essential to monitor for complications such as urinary tract infections and kidney stones.

References

NICE. (2024). Polycystic Kidney Disease: Diagnosis and Management. Retrieved from NICE
NHS. (2023). Polycystic Kidney Disease. Retrieved from NHS
British Association for Paediatric Nephrology (BAPN). (2022). Guidelines for the Management of PKD. Retrieved from BAPN
American Society of Nephrology (ASN). (2021). Polycystic Kidney Disease: Clinical Practice Guidelines. Retrieved from ASN