Polycystic Kidney Disease (ADPKD) — Written Clinical Reasoning

Model answer — Part A: the new diagnosis with preserved GFR

Confirm and frame. The imaging phenotype (bilateral enlarged kidneys, numerous cysts) in a man with an affected first-degree relative meets the unified ultrasound criteria — at 15–39 years, three or more cysts are diagnostic — so this is ADPKD, and the father's early ESKD suggests a PKD1-tempo family, though genotype should not be assumed aloud [1].

Baseline assessment, in sequence. Quantify blood pressure properly (home or ambulatory readings) because hypertension is the earliest and most modifiable driver; send creatinine with eGFR, urinalysis with albumin quantification, and a metabolic screen including uric acid; review the existing images for liver cysts; and take a three-generation family history that specifically asks about cerebral events, because aneurysm clustering would change his screening plan [4] [8].

Stage the progression. The key consultant move is to measure height-adjusted total kidney volume (MRI or CT) and plot it against age on the Mayo Imaging Classification — his kidneys are already markedly enlarged at 32, which suggests a rapid-progression class (1C–1E), and that class, not his reassuring creatinine, determines whether tolvaptan is worth discussing. eGFR is preserved by hyperfiltration at this stage and does not exclude rapid progression [3].

Counselling and management. Explain the diagnosis and its variability honestly — no fixed sentence; start an ACE inhibitor with a target below 110/75 mmHg as tolerated, the HALT-PKD target for young patients with preserved GFR [4]; advise a generous water intake of around 2–3 litres daily to suppress vasopressin [9]; counsel on salt, weight, NSAID avoidance and cardiovascular risk; arrange interval review of BP and renal function with re-measurement of kidney volume when it would change a decision; and open the family conversation — each child has a 50% inheritance risk, testing is offered with counselling (never imposed), and reproductive options including PGT can be explored with clinical genetics [7]. If he proves to be Mayo 1C–1E, the tolvaptan discussion follows the Part B framework [3] [5].

Model answer — Part B: the tolvaptan decision in rapid progression

Confirm the indication. She is a rapid progressor on two independent measures: Mayo class 1D (classes 1C–1E are rapid) and an eGFR slope of about 4–5 mL/min/1.73 m² per year. TEMPO 3:4 showed tolvaptan slowed kidney growth and eGFR decline in early CKD, and REPRISE extended the benefit to eGFR 25–65 — she sits squarely inside the combined evidence base, and guideline eligibility is met [5] [6] [7].

Weigh the burden honestly, in her context. Tolvaptan causes an obligatory aquaresis — several extra litres of urine daily — which for a long-haul flight attendant is a genuine occupational problem, not a footnote; it requires scheduled liver function tests (baseline, monthly for 18 months, then every 3 months) for the small risk of idiosyncratic hepatocellular injury, reversible on cessation; and it interacts with strong CYP3A inhibitors and requires sick-day rules for dehydration [5] [7]. The answer is not to decide for her but to quantify: benefit of slowed decline and delayed ESKD against daily polyuria, monitoring and cost — a shared decision, documented [5] [6].

The rest of the consultation is as important as the drug. Her sister's subarachnoid haemorrhage is a clear indication for MR angiography screening — family history of aneurysm/SAH is exactly the selective-screening trigger [8] [7]. Continue the ACE inhibitor toward target [4]. Survey extrarenal disease (liver cysts, valves on clinical grounds, hernias). Address her flying: if she starts tolvaptan, practical planning (aisle seat, fluid strategy, dose timing) or a change of duties may decide the matter as much as the evidence does [5]. And complete the family loop — her relatives' testing choices and her own reproductive history belong in the record [7].

What you would NOT do. Not withhold the drug because her GFR has already fallen (REPRISE is precisely her phenotype); not prescribe without the LFT monitoring plan; not screen everyone indiscriminately for aneurysms while missing the sister-triggered indication in front of you; and not neglect the occupational reality that will determine adherence [6] [8].