Renal & GU Board Prep for Family Medicine

Five-minute daily sessions on CKD management, electrolytes, UTIs, stones, and the urology a family physician actually handles.

Nephrology and urology together form a steady, mid-sized slice of the ABFM — smaller than cardiology, but dense with discrete decision rules that make questions easy to write and easy to miss. Chronic kidney disease alone touches a large fraction of a family medicine panel, and the exam expects you to stage it, slow it, dose around it, and know exactly when to refer it. The urology half is outpatient bread and butter: urinary tract infections, kidney stones, BPH, hematuria workups, and the prostate cancer screening conversation.

CKD questions have been reshaped by the same therapeutic shift that changed diabetes care: SGLT2 inhibitors now carry kidney-protection indications independent of glucose control, and finerenone has joined ACE inhibitors and ARBs in the albuminuria-lowering toolkit. The exam anchors on KDIGO staging — GFR category plus albuminuria category — because that grid drives everything: statin eligibility, nephrology referral, drug dosing, and how aggressively to chase blood pressure.

Electrolyte questions reward systematic thinking over memorized trivia. Hyponatremia stems walk you through volume status and urine studies; hyperkalemia stems test the treatment sequence (stabilize the myocardium, shift, then eliminate). These are among the most algorithm-friendly questions on the exam, which makes them reliable points once the algorithms are automatic.

On the urology side, precision matters more than depth. Nitrofurantoin fails below a GFR of 30. Asymptomatic bacteriuria is treated only in pregnancy and before urologic procedures. A 6 mm distal ureteral stone gets tamsulosin and time; a 12 mm stone gets urology. PSA screening is a shared decision for men 55 to 69, not a default order. The exam tests these lines exactly where clinicians blur them.

High-yield renal & genitourinary topics

• CKD staging and slowing progression. Stage by KDIGO: GFR categories G1 through G5 crossed with albuminuria categories A1 through A3. Slow progression with blood pressure control (target under 120 to 130 systolic per KDIGO/ACC), an ACE inhibitor or ARB for albuminuric disease, an SGLT2 inhibitor for most patients with CKD and albuminuria regardless of diabetes, and statin therapy for adults 50 and older with CKD.
• Nephrology referral criteria. Refer for GFR below 30 (G4 to G5), urine albumin-to-creatinine ratio of 300 mg/g or more that persists, rapid GFR decline (more than 5 mL/min per year), resistant hypertension on four agents, recurrent nephrolithiasis with CKD, persistent unexplained hematuria with renal features, or hereditary kidney disease. Late referral worsens dialysis outcomes and is a tested harm.
• Acute kidney injury: prerenal versus intrinsic versus postrenal. Prerenal: BUN-to-creatinine ratio above 20, FENa under 1 percent, improves with volume. Intrinsic (ATN): muddy brown casts, FENa above 2 percent, follows ischemia or nephrotoxins. Postrenal: obstruction — check a bladder scan or renal ultrasound, especially in older men with BPH. Hold ACE/ARB, NSAIDs, and diuretics during AKI; metformin pauses when GFR is acutely compromised.
• Hyponatremia workup and correction limits. Assess tonicity, volume status, urine osmolality, and urine sodium. High urine osmolality with euvolemia suggests SIADH (treat with fluid restriction); low urine osmolality suggests primary polydipsia or low solute intake. Correct chronic hyponatremia no faster than 8 mEq/L in 24 hours to avoid osmotic demyelination. Symptomatic severe hyponatremia gets hypertonic saline boluses.
• Hyperkalemia management sequence. With ECG changes: IV calcium first to stabilize the myocardium, then insulin with glucose (plus or minus beta-agonist) to shift potassium in, then elimination — loop diuretics, potassium binders (patiromer or sodium zirconium cyclosilicate), or dialysis. Review the med list: ACE/ARB, MRA, trimethoprim, and NSAIDs are the usual culprits in outpatient stems.
• UTI treatment across presentations. Uncomplicated cystitis: nitrofurantoin for five days, TMP-SMX for three days where local resistance is under 20 percent, or single-dose fosfomycin — avoid fluoroquinolones. Nitrofurantoin is ineffective below GFR 30. Pyelonephritis: fluoroquinolone or ceftriaxone-initiated regimens with culture guidance. Treat asymptomatic bacteriuria only in pregnancy or before invasive urologic procedures.
• Nephrolithiasis: acute management and prevention. Noncontrast CT is the diagnostic standard; ultrasound is preferred in pregnancy. Stones under 10 mm in the distal ureter without infection or obstruction can pass with analgesia and tamsulosin (medical expulsive therapy). Fever with an obstructing stone is an emergency requiring decompression. Prevention: high fluid intake, normal dietary calcium, low sodium; thiazides for recurrent calcium stones, citrate for hypocitraturia.
• BPH, PSA, and hematuria decisions. BPH: alpha-blockers (tamsulosin) work in days; 5-alpha-reductase inhibitors (finasteride) shrink larger glands over months and lower PSA by about half — double the measured value when screening. PSA screening is an individualized shared decision for men 55 to 69 (USPSTF grade C), not recommended at 70 and older. Gross hematuria or persistent microscopic hematuria with risk factors warrants CT urography plus cystoscopy.

ABFM exam tips

Learn the KDIGO grid, not just the GFR. Albuminuria category changes management as much as GFR does. A patient with GFR 55 and ACR 400 needs an ACE inhibitor or ARB, an SGLT2 inhibitor, and likely a nephrology conversation — while a GFR of 55 with normal albuminuria mostly needs monitoring and dose adjustments.

SGLT2 inhibitors are kidney drugs now. DAPA-CKD and EMPA-KIDNEY extended the indication beyond diabetes: CKD with albuminuria is itself the reason to prescribe. Expect the "what should be added" question where the patient is already on an ACE inhibitor — the answer is the SGLT2 inhibitor. A small initial GFR dip is expected and is not a reason to stop.

Calcium first in hyperkalemia with ECG changes. The sequence — stabilize, shift, eliminate — is tested in order. Insulin-glucose before calcium in a patient with peaked T waves is a wrong answer even though insulin "does more" for the potassium level.

Check the GFR before choosing a UTI drug. Nitrofurantoin below GFR 30 is the classic trap. So is TMP-SMX with an ACE inhibitor and borderline potassium, or in the first trimester of pregnancy. The stem hands you the creatinine for a reason.

Correct sodium slowly and know why. The number to memorize is a maximum of 8 mEq/L per 24 hours in chronic hyponatremia; overcorrection causes osmotic demyelination. If the vignette shows rapid correction underway, the answer often involves slowing it — sometimes with D5W or desmopressin.

Fever plus obstructing stone equals emergency. An infected, obstructed kidney needs urgent decompression (stent or nephrostomy), not medical expulsive therapy. This distinction between "watch and wait" stones and "call urology now" stones is a recurring discriminator.

Common pitfalls

Do not stop an ACE inhibitor for a small creatinine bump. A rise up to 30 percent after starting an ACE inhibitor or ARB is expected and acceptable — recheck, do not discontinue. Stopping renoprotection unnecessarily is a tested error; so is continuing it through true AKI or hyperkalemia above safe limits.

Do not screen for prostate cancer by default. PSA testing for men 55 to 69 is a grade C shared decision — the exam rewards discussing benefits and harms, not reflexively ordering it. Screening men over 70, or ordering PSA without discussion, are both wrong answers. Remember finasteride halves PSA.

Do not treat asymptomatic bacteriuria outside pregnancy and pre-procedure settings. This applies to older adults, patients with catheters, and patients with diabetes. Overtreatment drives resistance without benefit, and the exam tests restraint here repeatedly.

Do not image every first kidney stone the same way. Noncontrast CT for diagnosis, yes — but in pregnancy, ultrasound is first-line. And a young patient with a classic story and prior stones may reasonably be managed without repeat imaging. Radiation stewardship shows up in stems.

Do not miss postrenal AKI in older men. Rising creatinine plus lower urinary symptoms or a palpable bladder means get a bladder scan or ultrasound before anything fancy. Obstruction is the most reversible cause of AKI and the easiest to miss in a stem full of distractors.

Do not use FENa after diuretics. Loop diuretics invalidate FENa; use fractional excretion of urea instead. This small detail is a favorite way to separate memorized formulas from understanding.

Metformin and contrast: pause, do not panic. Current practice holds metformin around iodinated contrast when GFR is under 30 or AKI is present — not in everyone. Blanket "stop metformin for all scans" answers are outdated.

Frequently asked questions

What renal and GU topics are most tested on the ABFM?

CKD staging and progression-slowing therapy (ACE/ARB, SGLT2 inhibitors, blood pressure control), AKI classification, hyponatremia and hyperkalemia algorithms, UTI and pyelonephritis treatment, asymptomatic bacteriuria restraint, nephrolithiasis management, BPH pharmacotherapy, PSA shared decision-making, and hematuria workup. Drug dosing in renal impairment is threaded through the whole exam.

How much nephrology is on the ABFM exam?

The nephrologic and urogenital content areas each account for a modest single-digit percentage of the blueprint, but renal function affects drug-dosing and safety questions across every other category — so the effective footprint is larger than the label. The topics are also unusually algorithmic, which makes them efficient to master.

Are SGLT2 inhibitors really indicated for CKD without diabetes?

Yes. DAPA-CKD and EMPA-KIDNEY showed slower CKD progression and fewer kidney and cardiovascular events in patients with albuminuric CKD with or without diabetes, and KDIGO guidelines now recommend them broadly in CKD with albuminuria. Exams test this as an add-on to ACE inhibitor or ARB therapy, and expect you to tolerate the small initial GFR dip.

What is the fastest way to keep UTI treatment straight?

Anchor on three first-line cystitis options — nitrofurantoin five days, TMP-SMX three days, fosfomycin single dose — and their disqualifiers: GFR under 30 for nitrofurantoin, local resistance or sulfa issues for TMP-SMX. Fluoroquinolones are reserved for pyelonephritis and complicated infections. Pregnancy changes everything: screen, treat, and confirm cure.

When does a kidney stone need urology instead of watchful waiting?

Any sign of infection with obstruction (fever, sepsis) — that is an emergency needing decompression. Also stones larger than 10 mm, refractory pain or vomiting, solitary kidney, significant obstruction, or failure to pass after four to six weeks of medical expulsive therapy. Everything smaller and quieter gets fluids, analgesia, tamsulosin, and a strainer.

How does the exam handle PSA screening?

As a shared decision-making exercise. For men 55 to 69, USPSTF grade C means offer a conversation about benefits and harms rather than a default test; over 70, screening is not recommended (grade D). Questions reward eliciting patient values, and they test the finasteride-halves-PSA correction and the "do not biopsy a single mildly elevated PSA without repeating it" principle.

How should I study renal topics in five-minute daily sessions?

This category is built from algorithms — the hyperkalemia sequence, the hyponatremia tree, the KDIGO grid, UTI drug selection — and short daily repetitions are the most reliable way to make them automatic. Pair each algorithm with one or two applied questions per session so you practice extracting the deciding detail (GFR, urine studies, ECG changes) from the vignette.