Pathophysiology
P-II-11. Kidney disease, Case 3
腰疾患 症例3
Complaints:
- 27-year-old woman, at the emergency department
- For 2 days
- Progressive back pain
- T: 37.9 °C
- She vomited twice (in the last 6 hours)
- She suffered from cystitis 3 months ago
- Otherwise healthy
Diagnostic evaluation:
- Facial erythema
- T: 39.5 °C
- P: 120/min
- BP: 104/68 mmHg
- CV + Resp: normal
- Abdomen: painful all over, especially in the two lumbar regions
- Bowel sounds: normal
Laboratory (urine):
- Specific gravity: 1.020
- pH: 5–6
- WBCs/uL: > 500
- Nitrite: positive (strongly)
- Protein: 0.3–1 g/L
- Glucose: normal
- Ketones: negative
- UBG: normal
- Bilirubin: negative
- Hb (Ery/uL): ca. 50
Urine sediment: many bacteria, eumorphic erythrocytes, leucocytes, transitional epithelial cells.
Key Quotes & What They Tell Us
| Quote / Value | Interpretation |
|---|---|
| “Progressive back pain … especially in the two lumbar regions” | Flank/loin pain → upper urinary tract (kidney) involvement |
| T 39.5 °C; P 120/min; vomiting | Systemic infection (high fever, tachycardia) → distinguishes pyelonephritis from simple cystitis |
| Urine WBC > 500/µL; nitrite “positive (strongly)” | Pyuria with nitrites → bacterial (typically Gram-negative) urinary infection |
| Sediment: “many bacteria … leucocytes” | Confirms active bacterial infection of the urinary tract |
| “suffered from cystitis 3 months ago” | Prior lower UTI → ascending infection is the likely route |
| Protein 0.3–1 g/L; eumorphic erythrocytes | Mild proteinuria and non-glomerular (eumorphic) haematuria typical of infection, not glomerulonephritis |
Key Points
- Diagnosis: Acute pyelonephritis (upper urinary tract infection).
- Localizing features: Loin pain + high fever + systemic upset separate it from lower UTI/cystitis.
- Urine findings: Marked pyuria, strong nitrites, and bacteriuria confirm bacterial infection.
- Pathophysiology: Ascending infection from the bladder (recent cystitis) up the ureters to the renal parenchyma.
- Haematuria type: Eumorphic (non-glomerular) red cells — consistent with infection rather than a glomerular cause.
一問一答
▶What does urine WBC >500/µL (pyuria) signify?
An active inflammatory/infectious process in the urinary tract.
▶What does a strongly positive urine nitrite test indicate?
Bacteria (typically Gram-negative, e.g. E. coli) that reduce nitrate to nitrite — evidence of bacterial UTI.
▶What is the diagnosis in a young woman with 2 days of flank pain, high fever, vomiting, and pyuria with positive nitrites?
Acute pyelonephritis (an upper urinary tract infection).
▶What is the usual route of infection in acute pyelonephritis?
Ascending infection from the bladder up the ureters to the renal parenchyma.
▶What clinical features distinguish pyelonephritis from simple cystitis?
Loin/flank pain, high fever, tachycardia, and systemic upset (vomiting) indicate kidney involvement rather than a lower UTI.
▶Why does the recent episode of cystitis support the diagnosis?
A prior lower UTI predisposes to ascending spread of bacteria to the kidney.
▶What does eumorphic (normal-shaped) haematuria suggest about the cause?
A non-glomerular source (here infection), as opposed to dysmorphic red cells seen in glomerular disease.
▶Why does this patient have fever 39.5°C and tachycardia (P 120/min)?
A systemic inflammatory response to the renal bacterial infection.
▶Why does the mild proteinuria (0.3–1 g/L) occur in pyelonephritis?
Tubulointerstitial inflammation and pyuria cause mild protein leakage, not heavy glomerular proteinuria.
▶What is the most common causative organism of acute pyelonephritis?
Escherichia coli (a Gram-negative enteric bacterium).
▶Why are women more prone to ascending UTIs and pyelonephritis?
A shorter urethra and its proximity to the perineum facilitate bacterial entry into the bladder.
▶What white-cell finding on urine microscopy is characteristic of pyelonephritis vs cystitis?
White cell (leukocyte) casts indicate the inflammation originates in the kidney (upper tract).
▶What is a serious systemic complication of acute pyelonephritis?
Urosepsis (sepsis arising from the urinary tract infection).
▶What is the mainstay of treatment for acute pyelonephritis?
Prompt systemic (often empirical then culture-guided) antibiotics, plus fluids and supportive care.
▶Why is imaging considered if pyelonephritis fails to improve with antibiotics?
To detect obstruction, an abscess, or stones that would need drainage or removal.
▶Why is vomiting clinically important in this febrile patient?
It reflects systemic illness and threatens dehydration, and may require IV fluids/antibiotics.
▶Why does bilateral lumbar (loin) tenderness occur in pyelonephritis?
Inflammation and oedema stretch the renal capsule, causing flank pain/tenderness.
▶What chronic condition can result from recurrent pyelonephritis?
Chronic pyelonephritis with renal scarring, which may impair kidney function.
▶Why is a urine culture important even when the dipstick already suggests infection?
It identifies the organism and antibiotic sensitivities to guide targeted therapy.
▶Why does facial erythema/flushing accompany the high fever here?
Fever causes cutaneous vasodilation as part of the systemic febrile response.