The care of the patient with obesity and kidney disease sits between two fields, and much of it is trained deeply in neither general nephrology nor endocrinology/obesity medicine. This map lays out the ground it covers, organised around the CKM continuum.
Why a separate map
Nephrology fellowships train glomerular disease, dialysis, and transplant in depth but treat obesity mostly as a comorbidity; endocrinology and obesity-medicine training own incretin pharmacology but rarely the failing nephron. The clinically important material lives in the overlap.
Domain 01. Pathophysiology of the obesity–kidney axis
ORG (glomerulomegaly, adaptive hyperfiltration, secondary FSGS) — clinically atypical, usually subnephrotic proteinuria without hypoalbuminaemia, so under-recognised. The therapeutic hinge: weight reduction (bariatric or GLP-1/GIP) can drive proteinuria into remission — the general nephrologist lacks the pharmacotherapy and indication logic; the obesity physician does not read the biopsy. Renal hemodynamics and RAAS/sympathetic activation; adipokines, lipotoxicity, ectopic renal-sinus fat; uric-acid/fructose and gut-microbiome pathways; proposed weight-loss–independent renoprotection (magnitude debated); APOL1 and monogenic risk; the MASLD/MASH–CKD axis.
Domain 02. Diagnosis and risk stratification
Beyond BMI: body composition (DXA, bioimpedance), visceral adiposity, sarcopenic obesity; cystatin-C vs creatinine eGFR including the CKD-EPI 2021 combined equation; BSA-indexing vs de-indexing for dosing; measured GFR; hyperfiltration can mask early nephron loss. ORG histology (secondary FSGS with glomerulomegaly, perihilar sclerosis, milder foot-process effacement than primary FSGS) vs diabetic nephropathy and hypertensive nephrosclerosis, into which it is routinely misclassified — glomerular size must be correlated to body size. The biopsy itself is harder in obesity: greater skin-to-capsule distance, poorer ultrasound penetration, longer or CT-guided/transjugular needles, more non-diagnostic cores and bleeding.
Domain 03. Pharmacotherapy and renal safety
Agent- and endpoint-specific renal evidence: semaglutide in FLOW (kidney-outcome trial); tirzepatide kidney data exploratory/post-hoc (SURPASS-4, HR 0.58 [0.43–0.80]). Retatrutide investigational (TRANSCEND-CKD NCT05936151, topline 2026; TRIUMPH-Outcomes NCT06383390) — no reported phase-3 kidney-outcome results yet. SGLT2i and non-steroidal MRA (finerenone; FIDELIO/FIGARO). Emerging multi-pillar model. Renal-safety surveillance: GI losses with GLP-1/GIP (nausea, emesis, diarrhoea) causing hypokalaemia, metabolic alkalosis and prerenal AKI (a ‚triple whammy‘-type constellation; the classic term is RAS blocker + diuretic + NSAID); topiramate acidosis; oxalate nephropathy after malabsorptive surgery; bariatric metabolic sequelae (refeeding, thiamine, hypo-K/Mg/Ca, secondary hyperparathyroidism, vitamin-D deficiency). Rarer signals (e.g. SIADH-type hyponatraemia) belong in pharmacovigilance.
Domain 04. Nutrition and the protein dilemma
Reconciling weight loss and muscle preservation with protein restriction in advanced CKD; very-low-calorie diets; generally avoid unsupervised ketogenic diets in advanced CKD (electrolyte, acid–base, K+, phosphate, volume risks); preventing sarcopenia; behavioral medicine; weight regain and maintenance.
Domain 05. Metabolic and bariatric surgery
Effects on albuminuria, eGFR trajectory, CKD progression; candidate selection in CKD/ESKD; surgery as a bridge to listing; endoscopic options; postoperative oxalate nephropathy (esp. malabsorptive procedures such as Roux-en-Y, far less after sleeve), nephrolithiasis, AKI.
Domain 06. Transplantation
Pre-listing: BMI cut-offs (often 35–40) restrict access — an equity issue; bariatric surgery (esp. sleeve) as a bridge, with altered immunosuppressant absorption and nutritional sequelae; GLP-1 RAs increasingly used for pre-listing weight loss. Post-transplant: first-year weight gain is the rule; PTDM/NODAT with obesity as the main risk factor, potentiated by tacrolimus/steroids; recurrent or de-novo ORG in the graft; GLP-1 RAs in recipients (immunosuppression interactions barely charted); weight-based vs fixed immunosuppressant dosing and CNI PK; higher surgical complication rates. Living donation: the obese donor faces additive hyperfiltration (remnant plus obesity-driven).
Domain 07. The dialysis population
Hemodialysis: AVF creation harder with deep vessels (higher primary failure, transposition, difficult cannulation); the Kt/V ‚V problem‘ — urea distribution volume vs body weight, BSA- vs V-normalisation, which weight for dose and drug dosing; the obesity survival paradox (higher BMI, better HD survival) must be understood and muscle vs fat distinguished. Peritoneal dialysis — the sharpest intersection: glucose-based dialysate delivers a calorie load driving weight gain, hyperglycaemia and dyslipidaemia, so the therapy works against obesity management (steer with icodextrin and monitoring); catheter risk in a thick abdominal wall (leak, hernia, exit-site) and adequacy at large body volume. Intentional weight loss where needed for transplant access, mobility, metabolic complications, or PD mechanics.
Domain 08. Special populations
Pediatric CKD and transition; monogenic/syndromic obesity (Bardet–Biedl, Alström); APOL1 risk; pregnancy, preeclampsia, and pre-conception incretin considerations as data emerge; geriatric sarcopenic obesity; the onco-nephrology interface (obesity is a shared risk factor for several cancers, a signal the CKM framework flags).
Domain 09. Stone and bone metabolism
Obesity raises stone risk independently — uric-acid stones (low urine pH in insulin resistance) and calcium oxalate, coupled to metabolic syndrome. The bariatric paradox: Roux-en-Y drives enteric hyperoxaluria to oxalate stones and oxalate nephropathy/CKD (the therapy can injure the kidney); sleeve far less. 24-hour urine interpretation in metabolic context; CKD-MBD features specific to obesity; bone-health plans post-bariatric.
Domain 10. Integrated care, delivery and scholarship
Designing a multidisciplinary CKM clinic around the staging framework; implementation science and health equity; digital health and AI-assisted decision support (not yet validated for routine nephro-obesity care); pharmacovigilance (FAERS), registry and QI methods.
Each domain connects to the evidence: go to the study library →