14.1 GU and Renal Diagnosis and Management

The current FNP-BC Test Content Outline lists GU/Renal among the 13 body systems and genitourologic agents among the official drug classes. Domain II wants you to name cystitis, pyelonephritis, complicated infection, CKD, stone disease, BPH, incontinence type, and hematuria risk before you prescribe. Domain IV Implementation is the prescription, the hold on NSAIDs, and the same-day transfer when infection sits behind an obstruction.

Uncomplicated cystitis, pyelonephritis, and complicated UTI

Uncomplicated cystitis is an otherwise healthy nonpregnant woman with acute dysuria, frequency, and urgency, no fever, no CVA tenderness, and no vaginal discharge that suggests cervicitis or vaginitis. A dipstick that shows leukocyte esterase or nitrites supports the clinical diagnosis. You do not need a reflex culture on every first, straightforward episode.

Pyelonephritis adds systemic and upper-tract findings: fever, flank pain, CVA tenderness, nausea, or vomiting. The same organism has left the bladder and entered the parenchyma. These patients need a urine culture before antibiotics, a pregnancy test in anyone who can be pregnant, and a site-of-care decision. Stable, reliable adults who can take oral fluids may finish outpatient therapy after an initial parenteral dose when guidelines support it. Hypotension, intractable vomiting, pregnancy with systemic infection, obstruction, or a frail host belongs in the emergency department.

Complicated UTI is defined by the host and the anatomy, not by how miserable the patient feels. Treat as complicated when the patient is male, pregnant, catheterized, immunocompromised, or has stones, obstruction, poorly controlled diabetes, a recent instrumented tract, or known urologic abnormality. Complicated infection gets a culture, a longer and more carefully chosen course, and a search for the reason the tract is not ordinary.

Exam trap. A man with dysuria is never “uncomplicated cystitis.” Culture, consider STI in younger men, and look for obstruction or prostatitis. A pregnant woman with bacteria on culture is treated even when she feels well — asymptomatic bacteriuria in pregnancy is a pyelonephritis-prevention problem. The same colony count in a frail nursing-home resident without symptoms is usually not treated.

First-line drugs and when to culture

IDSA-style first-line therapy for uncomplicated cystitis is nitrofurantoin monohydrate/macrocrystals 100 mg twice daily for 5 days, TMP-SMX DS twice daily for 3 days when local E. coli resistance is known to be under about 20%, or fosfomycin 3 g as a single dose. Fluoroquinolones work, and that is exactly why they are not first-line: FDA warnings for tendon, aortic, CNS, and glucose harm, plus collateral damage to gut flora. Save them for when first-line agents cannot be used and the culture supports them.

Nitrofurantoin and fosfomycin do not reach reliable tissue levels in the kidney. If you have already decided this is pyelonephritis, those two drugs are the wrong class. Culture-directed beta-lactams or, when appropriate and after culture, TMP-SMX or a fluoroquinolone are the usual systemic choices — follow current IDSA language and local resistance rather than memorizing a single brand name.

Culture when the infection is complicated, the patient is pregnant, you suspect pyelonephritis, symptoms return within weeks, the patient is male, there is a catheter or recent instrumentation, or first-line therapy just failed. Recheck a test of cure in pregnancy. Recurrent cystitis — typically two infections in six months or three in a year — deserves a culture-confirmed pattern, a look at sexual timing and residual volume, and then a shared decision about postcoital or continuous prophylaxis after nonpharmacologic steps (hydration, postcoital voiding, vaginal estrogen in postmenopausal women).

CKD: stage it, protect the kidney, know when to refer

KDIGO stages CKD by cause, GFR category, and albuminuria category — not by a single creatinine. eGFR categories run G1 (≥90) through G5 (<15), with G3 split into G3a (45–59) and G3b (30–44). Albuminuria is A1 (<30 mg/g), A2 (30–299 mg/g), and A3 (≥300 mg/g) on a spot urine albumin-to-creatinine ratio. A 68-year-old with eGFR 52 and UACR 180 mg/g is G3a A2, not “a little high creatinine.” That pair of numbers changes blood-pressure drugs, diabetes drugs, and NSAID counseling.

Disease-modifying therapy in albuminuric diabetic CKD is an ACE inhibitor or ARB titrated to the highest tolerated dose plus an SGLT2 inhibitor with kidney-outcome data, unless a true contraindication exists. The SGLT2 inhibitor is there for the kidney and the heart, not only for the A1c. Expect a small, early dip in eGFR after ACEI/ARB or SGLT2 start; a rise in creatinine up to about 30% that then stabilizes is usually acceptable if potassium is safe. A larger jump, progressive decline, or potassium that will not stay below 5.5 mg/dL is a reason to hold, recheck volume and dual blockade, and call nephrology. Never combine ACEI plus ARB.

Avoid NSAIDs in CKD. They drop afferent flow, raise potassium with ACEI/ARB, and turn a G3 kidney into an acute-on-chronic admission after a dental extraction. Counsel every CKD chart the same way you counsel warfarin. Hold metformin as eGFR falls through the mid-30s and stop it below 30; adjust or avoid other renally cleared drugs.

Refer when the eGFR trajectory is steep (a drop of more than about 5 mL/min/1.73 m² per year, or a 25% fall from baseline), when eGFR is below 30, when the cause is unclear, when the sediment is active (RBC casts, heavy proteinuria that looks glomerular), when blood pressure or potassium will not come under control, or when you need help planning kidney-replacement therapy. Do not wait for G5 to introduce the nephrologist.

Nephrolithiasis

Most acute flank-pain stones are calcium-based. The highest-yield imaging question is CT versus ultrasound. Noncontrast CT is the most sensitive test in a nonpregnant adult when you must confirm or exclude a stone and look for obstruction. Ultrasound is first-line in pregnancy and is a reasonable radiation-sparing first test when the story is classic and you only need to know whether hydronephrosis is present. Strain the urine. Send recovered stone for composition. Analgesia and antiemetics come first; NSAIDs are effective if the kidney can tolerate them.

Medical expulsive therapy with an alpha-blocker (typically tamsulosin) is reserved for selected distal ureteral stones, generally in the 5–10 mm range, in a patient you can follow. Tiny distal stones often pass without a drug. Stones larger than 10 mm, proximal stones, and anyone who cannot keep down fluids need urology, not another week of tamsulosin hope.

Red flags: fever or infection plus obstruction is an emergency — the kidney is an abscess waiting to happen and needs urgent decompression (stent or nephrostomy) plus antibiotics, not an office fluoroquinolone and a follow-up slot next Thursday. Anuria, a solitary kidney, intractable pain or vomiting, and pregnancy with obstruction also leave the clinic for the emergency department.

Prevention after a first stone is not a mystery vitamin. Push 2.5–3 L of fluid a day, cut sodium, and use 24-hour urine results to choose a thiazide for hypercalciuria, potassium citrate for hypocitraturia, or allopurinol for hyperuricosuria. Do not tell every stone former to stop all calcium — dietary calcium is usually continued.

BPH, incontinence, and hematuria

BPH is a quality-of-life diagnosis until it is a safety diagnosis. Score symptoms with the AUA Symptom Index (IPSS): 0–7 mild, 8–19 moderate, 20–35 severe. Ask about bother, nocturia, and retention (overflow dribbling, a bladder you can palpate, post-void residual that is high). An alpha-blocker (tamsulosin, alfuzosin, silodosin) is first-line for bother; counsel orthostasis and intraoperative floppy-iris syndrome. Add a 5-alpha-reductase inhibitor (finasteride or dutasteride) when the gland is large (prostate volume ≳30 g or PSA suggesting volume, often >1.5 ng/mL). 5-ARIs take about six months, shrink the gland, and halve the measured PSA — double the number when you interpret it. Combination therapy is reasonable for a large, symptomatic gland. Refer for hematuria, acute retention, recurrent infection or stones, a nodular or asymmetric prostate, a rising PSA that is not explained by the 5-ARI math, or failed medical therapy.

Incontinence is typed before it is medicated. Stress leaks with cough, laugh, or lift — first-line is pelvic-floor physical therapy, weight loss, and a pessary when anatomy helps. Urge (overactive bladder) is urgency, frequency, and nocturia — bladder training, timed voiding, and caffeine cutback come before an antimuscarinic or a beta-3 agonist, and you check a post-void residual so you do not turn urge into overflow. Overflow is incomplete emptying from obstruction or a neurogenic bladder — treat the obstruction or teach catheterization; an anticholinergic here makes it worse. Functional incontinence is a mobility, cognition, or toilet-access problem — fix the room and the schedule. Every new leak gets a urinalysis, a residual, and a bladder diary before a prescription.

Hematuria in adults is not a “period of observation.” Confirm microscopic hematuria as ≥3 RBC/HPF on microscopy, not dipstick alone. Gross hematuria is a urology referral even if it happened once and the patient feels fine. Do not blame anticoagulation or antiplatelet therapy and stop. Sort glomerular clues (RBC casts, heavy proteinuria, dysmorphic RBCs, rising creatinine) to nephrology. Everyone else is risk-stratified by age, smoking, degree of hematuria, and occupational exposures and then gets the imaging-plus-cystoscopy pathway AUA describes. Treat a documented UTI and recheck; persistent blood after the infection clears still needs a cancer-aware workup. The exam trap is sending a 62-year-old who smokes home because “the dipstick was only 1+.”

FNP traps: treating pyelonephritis with nitrofurantoin; writing ciprofloxacin for a first uncomplicated cystitis; ignoring a man or a pregnant patient as “simple UTI”; leaving albuminuric diabetic CKD on NSAIDs without ACEI/ARB or SGLT2; watching fever and an obstructing stone in clinic; starting a 5-ARI for a small prostate and reading the halved PSA as a cure; and filing adult hematuria under “watchful waiting.”