Polycystic Kidney Disease (PKD)

PKD is caused by mutations in the PKD1 or PKD2 genes, which produce proteins that help kidney tubules maintain their structure. When these proteins are faulty, tubule cells proliferate abnormally and secrete fluid, forming cysts. Cysts enlarge year by year, compressing neighbouring nephrons and triggering inflammation and scarring (fibrosis). By age 60, about 50% of people with ADPKD have reached kidney failure. The PKD1 form progresses faster than PKD2.

PKD is usually suspected when an adult has enlarged kidneys, high blood pressure, or a family history. Ultrasound is the first test. In at-risk adults (aged 15–39), the presence of at least 3 renal cysts (unilateral or bilateral) is highly suggestive. Genetic testing confirms the diagnosis and can identify at-risk relatives before symptoms begin. NHS genetic counselling is available for families considering testing.

Tolvaptan (Jinarc) is a vasopressin V2-receptor antagonist that reduces cyst growth by blocking water reabsorption in the collecting duct. NICE TA358 recommends tolvaptan for adults with ADPKD who have rapidly progressing disease (eGFR > 25 but declining, or total kidney volume > 750 ml by MRI). It is taken as a tablet twice daily. Side effects include increased thirst and urination, and liver enzyme elevations — so regular blood monitoring is required.

In PKD, high blood pressure starts early and accelerates kidney damage independently of the cysts. UK targets are usually < 130/80 mmHg if tolerated. ACE inhibitors or ARBs are first-line because they also reduce proteinuria. A low-salt diet (under 5 g/day), regular exercise, weight management, and limiting alcohol all help. Home blood pressure monitoring is strongly encouraged.

• Salt: under 5 g/day — the single most impactful dietary change.
• Water: drink enough to keep urine pale yellow — your nephrologist may suggest 2–3 litres daily if not fluid-restricted.
• Caffeine: limit to 1–2 cups of tea or coffee daily; avoid energy drinks. Early data suggests caffeine may stimulate cyst growth via cAMP.
• Protein: a moderate intake (0.8–1.0 g/kg/day) is sensible — not high-protein diets.
• NSAIDs: avoid ibuprofen and naproxen; use paracetamol for pain instead.
• Smoking: stop — it accelerates kidney decline and cardiovascular risk.

PKD can affect other organs. Up to 10% of adults with ADPKD develop brain aneurysms (berry aneurysms), which can rupture and cause a subarachnoid haemorrhage. Screening with MR angiography is recommended for those with a family history of aneurysm or stroke. Liver cysts are common but rarely cause problems. Abdominal hernias and diverticular disease are also more frequent.