Case 08: The Sore Throat That Came Back

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Session S3 · 2026-10-28 · in-session · 37 min Anchor: Hematuria and nephritic syndrome that becomes RPGN (IgA vs post-infectious; lupus; ANCA; anti-GBM) · Integrates: Glomerular vs urologic hematuria routing, AKI staging and the invalid eGFR, AEIOU and hyperkalemia with AKI, ACEi contraindications and the pregnancy test, pediatric BP and HSP (warm-up) One-line hook: Cola-colored urine on day two of a sore throat reads like textbook IgA nephropathy — until she comes back three weeks later and every result has to be read again. A new PA will see this exact sequence. The skill is knowing which visit is the emergency.

Author: Andrew Bland, MD, FACP, FAAP — Medical Associates Dept of Nephrology | UICOMP | UDPA | Butler COM. Fictional patient.

Learning Objectives

Answers for this section: W1 · W2 · W3 · Q4 · Q5 · Q6 · Q7 · Q8 · Q9 · Q10 · Q11 · Q12

• Define microhematuria by microscopy (≥3 RBC/hpf on a properly collected specimen, never by dipstick alone) and route it: dysmorphic red cells, acanthocytes, RBC casts or proteinuria go to nephrology; isomorphic cells with urothelial-cancer risk factors go to urology.
• Separate synpharyngitic IgA nephropathy from post-infectious glomerulonephritis using timing and the C3/C4 pattern, and name the supportive care and referral pace for each.
• Recognize rapidly progressive glomerulonephritis (a creatinine moving over days to weeks plus an active sediment), stage the AKI with KDIGO 2012, explain why the printed eGFR is invalid, send the stat serology panel, and call nephrology the same day without waiting for a biopsy.
• Manage what rides along with glomerular AKI at student level: pair the potassium with the ECG, run the AEIOU check, control blood pressure with a pregnancy test before any ACEi or ARB, and stop the NSAID.
• State that biopsy and immunosuppression are nephrology's decisions and that uncontrolled blood pressure is treated before a biopsy (other contraindications and the lupus every-visit checks are discussed in the Resolution, not tested).

Warm-Up (individual commit before the case)

Answers for this section: W1 · W2 · W3

Three readiness items. Cards up, no discussion yet; they check that the prerequisites are in the room.

Part 1 — Presentation

Answers for this section: Q4 · Q5

Visit 1 — a Tuesday afternoon in student health, late October.

Lena is 19, a sophomore, and she is embarrassed to be here. Two days ago her throat started to hurt — scratchy, then raw, worse on swallowing. Low fever last night. This morning her urine was the color of cola. No pain with urination, no flank pain, no clots. She has never had blood in her urine before, never been told her blood pressure was high, and has never had blood work done ("I've never been sick enough"). She rows for the club team, drinks on weekends, does not smoke or vape, and has no family history of kidney disease, deafness or lupus. Her last period was two weeks ago and regular on her pill.

She took ibuprofen around the clock for the throat.

Vitals: BP 148/92 (repeated, seated, right arm, 146/90) · HR 84 · T 38.1 °C (100.6 °F) · RR 16 · SpO₂ 99% room air · weight 61 kg · height 165 cm.

Exam: Pharynx red without exudate, tender anterior cervical nodes. No rash. No joint swelling. No periorbital or ankle edema. Lungs clear. Heart regular, no murmur. Abdomen soft, no flank tenderness. Rapid strep antigen in the office: negative.

Office dipstick: blood 3+, protein 2+, leukocyte esterase negative, nitrite negative, glucose negative.

Three facts sit in that stem that a new PA has to hold at once: a febrile pharyngitis, a blood pressure of 148/92 in a 19-year-old rower, and a dipstick that says blood and protein. The first question is whether that dipstick is even hematuria.

Pause — commit before the reveal

Part 2 — Data

Answers for this section: Q6 · Q7 · Q8

Visit 1 laboratory results (same afternoon).

Urinalysis with microscopy (fresh clean-catch, read within 30 minutes).

Read it the way the chapter teaches: are the red cells deformed, and are there casts? Both. Acanthocytes at 12% are above the 5% threshold that Köhler found 98% specific for glomerular bleeding, and red cell casts prove the cells were inside the nephron. Protein 1.2 g/g — real, but under the nephrotic 3.5 g/g line. Blood pressure up. Creatinine 1.0 — at the upper limit for a woman, and the lab's own eGFR of 83 is below its >90 reference. In a 19-year-old that may be a rower's muscle mass or a 30% loss of filtration; with no prior value, nobody can say which. That uncertainty is one more reason the call happens today.

That is the nephritic pattern: hematuria with casts, sub-nephrotic proteinuria, hypertension, and a kidney that may or may not be losing function. The nephrotic pattern is the other animal — more than 3.5 g of protein a day, albumin under 3, edema, high cholesterol, and a sediment that is bland except for fat. She is nephritic.

And the complements are normal.

What actually happened. Nephrology took the call, agreed with the IgA working diagnosis, and asked that the ANA, ANCA and anti-GBM go on the same slip as the 72-hour creatinine and UPCR — one draw, one trip to the lab — with a clinic visit in two weeks. Nephrology deferred an antihypertensive to the 72-hour visit, to re-measure off the NSAID — a visit that never happened. Lena's throat got better in four days. The urine cleared to its usual color. The lab slip for the 72-hour draw, serology and all, went in her backpack. Midterms came. The clinic referral went by fax and no one owned the follow-up.

Visit 2 — three weeks later, the same clinic, a Monday morning.

She comes back because she cannot get out of bed. Two weeks of fatigue that sleep does not fix. Wrists, knuckles and knees ache and feel stiff for an hour every morning. A rash across both cheeks and the bridge of her nose came up after a weekend outside and has not faded; it skips the folds beside her nose. Low fevers in the evenings. She has been taking naproxen for the joints for eight days. Her urine is dark again and she thinks she is making less of it. Her weight is 63 kg — up 2 kg. No cough, no hemoptysis, no shortness of breath, no chest pain. No sinus pain, no nosebleeds. No new medications besides the naproxen.

Vitals: BP 158/98 (repeat 156/96) · HR 88 · T 37.9 °C · RR 18 · SpO₂ 98% room air.

Exam: Malar rash sparing the nasolabial folds. One shallow painless ulcer on the hard palate. Mild synovitis at both wrists and the second and third MCP joints; knees without effusion. Trace bilateral ankle edema. Lungs clear, no crackles. Heart regular, no rub, no murmur. No JVD. Alert, oriented, no asterixis (the flapping hand tremor of uremia). Abdomen soft.

Visit 2 laboratory results (drawn 10:15, resulted by noon).

Urinalysis with microscopy (fresh clean-catch, read within 30 minutes) — visit 2 beside visit 1.

The arithmetic first, because the room will reach for the eGFR. Anion gap 137 − (107 + 18) = 12; her albumin is 3.2, so add 2.5 × 0.8 = 2 → corrected gap 14. A mild acidosis of falling filtration — retained acid plus bicarbonate the kidney is no longer regenerating. BUN:creatinine 18, not the >20 of a dry patient; she is not dry. White count down, hemoglobin down, platelets down — three cell lines moving the wrong way in three weeks. And a creatinine that has gone from 1.0 to 2.4.

Pause — commit before the reveal

Part 3 — Course and Decisions

Answers for this section: Q9 · Q10 · Q11

Nephrology saw her at 15:40 the same day and admitted her to a monitored medical bed. Urine output on the ward 35 mL/h (about 0.55 mL/kg/h at 63 kg). The chest film was clear with a normal heart size. Renal ultrasound: right kidney 11.8 cm, left 12.1 cm, mildly echogenic cortex, no hydronephrosis, post-void residual 25 mL. Repeat chemistry and ECG ordered for 16:00 and 06:00.

The panel came back over the next 36 hours, the complements first. Three weeks ago both were normal and the room — correctly, on the evidence it had — called this IgA nephropathy.

The rest of the panel:

Now both complements are low, the ANA strongly positive, the anti-dsDNA ten times the upper limit. The sore throat did not come back. Something else did.

The diagnosis has changed. Her potassium has not waited for it.

Pause — commit before the reveal

Counterfactual — discuss, no cards. Had Lena arrived at visit 2 coughing up blood, what changes? Hemoptysis plus a glomerular AKI is the pulmonary-renal syndrome, and it narrows the differential to two serologies that must be drawn together: ANCA and anti-GBM. c-ANCA with PR3 points to granulomatosis with polyangiitis (sinuses, lungs, kidneys); p-ANCA with MPO points to microscopic polyangiitis (lungs and kidneys, no upper airway). Anti-GBM disease — Goodpasture syndrome when the lungs are involved — is the glomerulonephritis where nephrology starts plasma exchange on the serology, before the biopsy, because the antibody is the disease and the lungs can bleed fatally. The student's job does not change: send both antibodies with the rest of the panel, get the chest film, and say "pulmonary-renal syndrome" on the phone. Nothing about plasma exchange, its dose or its duration is a student decision. Her chest film was clear and both antibodies were negative — but the panel was sent as if they might not be. → Vasculitis and Complement-Mediated GN student handout — III. Anti-GBM Disease · Course reading: Vasculitis and Complement handout — Anti-GBM Disease (Goodpasture Syndrome)

Self-study checkpoint — after class

Answers for this section: Q12

This additional question is completed after class and does not extend the timed run sheet.

Resolution and Teaching Points

Answers for this section: W1 · W2 · W3 · Q4 · Q5 · Q6 · Q7 · Q8 · Q9 · Q10 · Q11 · Q12

Naproxen was stopped on admission, a potassium-restricted diet was ordered, and amlodipine 5 mg was started that evening after the negative hCG. Day 2: BP 136/84 on amlodipine, platelets 142, INR 1.0, no anticoagulants, two 12-cm kidneys — nephrology biopsied her that afternoon. Creatinine peaked at 3.1 on day 3 — 3.1× her known value, stage 3 at the peak, exactly the restaging Q7 promised — and started down. The biopsy showed a proliferative lupus nephritis; nephrology and rheumatology started glucocorticoids, a second immunosuppressant (mycophenolate) and hydroxychloroquine — the class names are the student's to know, the doses are not. Potassium was 4.6 at discharge on day 5 with a creatinine of 2.6 and falling. The combined pill was stopped on admission — estrogen is avoided in active nephritis, uncontrolled hypertension and nephrotic-range proteinuria — and contraception was reviewed with rheumatology and gynecology before discharge; she left on a progestin-only method, with a levonorgestrel IUD arranged.

Week 6 in nephrology clinic: creatinine 1.6, potassium 4.4, urine hCG negative again, contraception confirmed (IUD placed) — lisinopril started. Month 3: creatinine 1.2, UPCR 0.9 g/g, C3 88, C4 15, anti-dsDNA 96 and falling, BP 124/78. She is back on the water with the rowing team. Every visit, for the rest of her life with this disease, gets the same three things: a urinalysis, a UPCR and a creatinine — because lupus nephritis declares itself in the urine before it declares itself anywhere else.

The sore throat never came back. It was a viral pharyngitis that unmasked a disease already underway, and a creatinine of 1.0 — the upper limit, with no baseline to judge it against — beside casts on day two was the first chance to catch it. The second chance was a 72-hour lab slip that no one owned.

Clinical Pearl — Hematuria is a microscope word Three or more red cells per high-power field on a properly collected specimen. The dipstick cannot distinguish red cells from hemoglobin or myoglobin, and it cannot see shape or casts. Acanthocytes at or above 5% are 98% specific for glomerular bleeding; red cell casts prove the cells were inside the nephron. Their absence excludes nothing — sensitivity runs 20–52%.

Clinical Pearl — Two diseases, two clocks Cola urine within 1–3 days of a sore throat is synpharyngitic IgA nephropathy. Post-infectious GN follows pharyngitis by 1–3 weeks and impetigo by 3–6 weeks, runs a low C3 with a normal C4; the C3 normalizes within 6–8 weeks in most patients, and a C3 still low at 12 weeks is no longer post-infectious GN until proven otherwise.

Clinical Pearl — Read the complement pattern before the names Both low → classical pathway: lupus, cryoglobulinemia, endocarditis, MPGN. Low C3 and normal C4 → alternative pathway: post-infectious GN, C3 glomerulopathy. Both normal → IgA nephropathy, ANCA vasculitis, anti-GBM disease. Read the C4 before you move the hypothesis.

Clinical Pearl — RPGN is a tempo, and the eGFR cannot keep up A creatinine rising over days to weeks with an active sediment is RPGN until proven otherwise. Stage it by the creatinine ratio (KDIGO 2012), write "eGFR not valid — creatinine is moving," send ANCA (PR3/MPO), anti-GBM, ANA/anti-dsDNA, C3/C4, blood cultures, a chest film and a renal ultrasound, and call nephrology today. Do not wait for the biopsy to send the serology; do not wait for the serology to make the call.

Clinical Pearl — Before any ACEi or ARB Before ACEi/ARB initiation, assess pregnancy potential and counsel about fetal risk, review potassium and kidney function, and plan laboratory follow-up. In this case pregnancy testing is already negative, but K 5.6 and worsening AKI justify deferral. A potassium number is a context-dependent prescribing decision, not a stand-alone universal rule.

Pitfall — The referral form that was supposed to be a phone call Red cell casts or acanthocytes with proteinuria sit in the same-day row of the referral table even when the creatinine is 1.0, because day two does not tell you where day five will be. A fax is not a handoff. Someone owns the 72-hour labs — serology included — and it is the clinician who ordered them.

Pitfall — Treating the number instead of the patient "eGFR 29" on a moving creatinine is not CKD G4. Potassium 5.6 with a normal ECG is not an indication for calcium, and it is not the "E" of AEIOU — that is refractory hyperkalemia or hyperkalemia with ECG changes. Both reflexes come from reading a printout instead of the trend and the tracing.

Concept Links

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Assigned reading: the explanations in this case and the question-linked course evidence guide. The objective map distinguishes tested decisions from concepts taught in explanations.

Concepts: aki-01, aki-02, aki-22, aki-24, glom-02, glom-03, glom-06, glom-07, glom-12, glom-13, glom-14, glom-15, glom-16, glom-17, glom-23, htn-cardiorenal-08, htn-cardiorenal-17.