Anuria detail nephro, also give reference of Harrison 22nd
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Anuria - Detailed Nephrology Review
Definition
Anuria is the complete absence (or near-complete cessation) of urine formation, defined as urine output < 100 mL/24 hours. It is distinct from:
- Oliguria: urine output < 400 mL/24 hours
- Nonoliguria: urine output > 400 mL/d despite azotemia
"Oliguria refers to a 24-h urine output <400 mL, and anuria is the complete absence of urine formation (<100 mL)."
- Harrison's Principles of Internal Medicine, 22nd Edition, Chapter 55 (Oliguria and Anuria section)
Key distinction from urinary retention: In anuria, the kidneys do not excrete urine - the bladder is empty. In retention, urine is formed but cannot be voided - the bladder is full and distended. - S Das Manual on Clinical Surgery, 13th Ed.
Causes - The Classic Triad (Pre-Renal / Renal / Post-Renal)
1. Pre-Renal Causes
Reduced renal perfusion without intrinsic kidney damage initially. If prolonged, progresses to intrinsic injury.
- Hypovolemic shock (hemorrhage, severe burns, dehydration, diarrhea, vomiting)
- Cardiogenic shock (pump failure)
- Septic shock
- Third-spacing (pancreatitis, bowel obstruction, major trauma)
- Intra-abdominal hypertension - anuria develops when intra-abdominal pressure reaches approximately 30 mmHg (41 cm H2O)
- Hepatorenal syndrome (type 1 - rapid onset; oliguria more common with type 1)
- Renal artery stenosis + ACE inhibitor/ARB initiation (AKI from loss of efferent arteriolar tone)
2. Intrinsic Renal (Parenchymal) Causes
Vascular:
- Renal artery dissection or complete occlusion (vascular catastrophe)
- Renal vein thrombosis (bilateral or of a single functioning kidney)
- Malignant hypertension
- Hemolytic-uremic syndrome (HUS) / Thrombotic thrombocytopenic purpura (TTP)
Glomerular:
- Severe rapidly progressive glomerulonephritis (RPGN / crescentic GN)
- Severe acute nephritic syndrome
- ANCA vasculitis
Tubular:
- Severe acute tubular necrosis (ATN) - ischemic or nephrotoxic
- Renal cortical necrosis (most severe form of ATN, often in obstetric catastrophes)
- Cast nephropathy in multiple myeloma (Bence Jones proteins)
- Myoglobinuric AKI (crush syndrome, rhabdomyolysis)
- Acute hemolysis / incompatible blood transfusion
Interstitial/Other:
- Severe acute interstitial nephritis (AIN)
- Pyelonephritis / pyonephrosis (severe bilateral)
- Renal tuberculosis
Drug-related combination:
- Combined therapy with NSAIDs + ACE inhibitors and/or ARBs - a classic triad causing anuria by blocking prostaglandin-mediated afferent arteriolar dilation, angiotensin II-mediated efferent tone, and aldosterone signaling simultaneously.
"Anuria can be caused by complete bilateral urinary tract obstruction; a vascular catastrophe (dissection or arterial occlusion); renal vein thrombosis; acute cast nephropathy in myeloma; renal cortical necrosis; severe ATN; severe rapidly progressive glomerulonephritis; combined therapy with NSAIDs, ACE inhibitors, and/or ARBs; and hypovolemic, cardiogenic, or septic shock."
- Harrison's Principles of Internal Medicine, 22nd Edition, Chapter 55
3. Post-Renal (Obstructive) Causes
Requires bilateral obstruction, or unilateral obstruction of a single functioning kidney (e.g., transplant kidney).
- Bilateral obstructing ureteric calculi (calculous anuria)
- Bilateral ureteric ligation (accidental - e.g., during hysterectomy)
- Massive bladder outlet obstruction (prostatic hypertrophy, prostate cancer)
- Cervical cancer, lymphoma, retroperitoneal fibrosis compressing ureters
- Clot retention / large transitional cell carcinoma
- Bilateral ureteric obstruction from any pelvic/retroperitoneal malignancy
"Alternating oliguria and anuria (the latter defined as less than 100 mL/24 hr) is a classic indicator of intermittent obstruction, which occurs as urine collects behind an obstructing stone or tumor and then is allowed to flow past as the obstructing material shifts position."
- Rosen's Emergency Medicine
"Complete bilateral obstruction or unilateral obstruction of a single functioning kidney such as a kidney transplant will result in anuria. However, in partial obstruction, the urine output may be normal or increased (polyuria). A pattern of alternating oliguria and polyuria or the presence of anuria strongly suggests obstructive uropathy."
- Comprehensive Clinical Nephrology, 7th Edition
Pathophysiology
Why Is Oliguria/Anuria Never Normal?
"Oliguria is never normal, since at least 400 mL of maximally concentrated urine must be produced to excrete the obligate daily osmolar load."
- Harrison's Principles of Internal Medicine, 22nd Edition
Renal Capsule Effect in AKI
When the kidney becomes edematous in AKI, the renal capsule limits swelling, raising renal interstitial pressure. This decreases GFR and is thought to perpetuate and prolong anuria. - Ganong's Review of Medical Physiology, 26th Ed.
Non-oliguric vs. Oliguric AKI
Nonoliguria (urine output > 400 mL/d despite azotemia) carries a better prognosis:
- Electrolyte disturbances (hyperkalemia, acidosis) are less severe
- Recovery to normal renal function is usually faster
- Harrison's 22nd Edition
KDIGO Staging (Anuria in Context)
| Stage | Serum Creatinine | Urine Output |
|---|---|---|
| 1 | 1.5-1.9x baseline or ≥0.3 mg/dL rise | < 0.5 mL/kg/h for 6-12 h |
| 2 | 2.0-2.9x baseline | < 0.5 mL/kg/h for ≥12 h |
| 3 | ≥3x baseline or ≥4.0 mg/dL or RRT | < 0.3 mL/kg/h for ≥24 h or anuria ≥12 h |
Anuria for ≥12 hours = KDIGO Stage 3 (most severe). - Barash Clinical Anesthesia, 9th Ed. / Braunwald's Heart Disease
Clinical Assessment
History
- Recent hypotensive episode, surgery, trauma, nephrotoxin exposure
- Prostatic symptoms, pelvic malignancy, prior renal calculi
- Drug history (NSAIDs, ACE-I/ARBs, aminoglycosides, contrast)
- Systemic disease: diabetes, myeloma, vasculitis, SLE
Examination
- Bladder fullness (catheterize immediately to exclude retention)
- Flank tenderness (obstruction, pyelonephritis)
- Volume status assessment (JVP, skin turgor, mucous membranes)
- Signs of systemic disease (purpura, rash, organomegaly)
Key Lab Investigations
| Investigation | Pre-Renal | Intrinsic Renal | Post-Renal (Early) |
|---|---|---|---|
| Urine Na (mmol/L) | < 20 | > 40 | < 20 (early) → rises |
| FENa | < 1% | > 2% | < 1% (early) |
| Urine osmolality | > 500 | < 350 | > 500 (early) |
| Urine:plasma creatinine | > 40 | < 20 | Variable |
| Urinary sediment | Bland / hyaline casts | Granular/muddy brown casts (ATN), RBC casts (GN), WBC casts (AIN) | Normal / hematuria |
In the acute phase of obstruction, urinary electrolytes mimic prerenal state (low urinary Na < 20 mmol/L, FENa < 1%, high osmolality > 500 mOsm/kg). With prolonged obstruction, concentrating ability is lost and sodium reabsorption fails, giving rise to post-obstructive diuresis on relief. - Comprehensive Clinical Nephrology, 7th Ed.
Imaging
- Urgent renal ultrasound: first-line - identifies hydronephrosis (obstructive), kidney size (CKD vs AKI), bladder distension
- Bladder catheterization: large residual volume confirms lower urinary tract obstruction (prostatic, neurogenic)
- CT abdomen/pelvis: better delineation of ureteric calculi, retroperitoneal masses
- Doppler USS: renal artery/vein assessment
- Postrenal AKI should be considered when urine output < 450 mL/day (oliguria) or < 100 mL/day (anuria) - Goldman-Cecil Medicine
Management Principles
1. Immediate Steps
- Catheterize the bladder - always first, to exclude retention and measure true urine output
- Establish IV access; begin volume assessment
- Urgent electrolytes, BMP, urinalysis with microscopy, urine electrolytes
2. Treat the Underlying Cause
Pre-renal: Prompt intravenous fluid resuscitation (crystalloids preferred); careful monitoring in elderly, heart failure, cirrhosis. Avoid aggressive overload - can precipitate pulmonary edema.
Post-renal obstruction:
- Lower tract (prostate): urethral catheter, followed by definitive surgery
- Upper tract (ureteric stone/tumor): ureteral stenting or percutaneous nephrostomy
Intrinsic renal:
- Stop nephrotoxins
- Treat underlying cause (immunosuppression for RPGN/vasculitis, plasmapheresis for TTP/HUS)
- General supportive care:
- Maintain fluid balance; daily IV furosemide (40-80 mg IV) for volume overload
- Hyperkalemia: sodium zirconium cyclosilicate (Lokelma) or patiromer + low-K diet
- Metabolic acidosis: NaHCO3 tablets
- Hyperphosphatemia: oral phosphate binders
- Hypocalcemia: calcium supplements
- Restrict dietary sodium, potassium, protein
3. Renal Replacement Therapy (RRT) - Dialysis Indications
Classic AEIOU indications:
| Indication | Details |
|---|---|
| Acidosis | Severe metabolic acidosis unresponsive to bicarbonate |
| Electrolytes | Refractory hyperkalemia (K+ > 6.5 or with ECG changes) |
| Intoxication | Dialyzable toxins (methanol, ethylene glycol, salicylates, lithium) |
| Overload | Fluid overload refractory to diuretics |
| Uremia | Uremic encephalopathy, pericarditis, bleeding |
- Anuria itself, when persistent and combined with any of the above, is an indication for RRT
- Options include hemodialysis (HD), continuous RRT (CRRT) in hemodynamically unstable patients, or peritoneal dialysis (PD)
Anuria in Peritoneal Dialysis (PD) Patients
Anuric patients can be managed on PD, particularly with automated PD (APD). They often require one or more additional daytime exchanges. Peritoneal membrane function should be closely monitored. Residual kidney function (RKF) predicts survival even in PD patients. - NKF Primer on Kidney Diseases, 8th Ed.
Harrison's 22nd Edition - Direct Reference
Book: Harrison's Principles of Internal Medicine, 22nd Edition (2025, McGraw-Hill Medical)
ISBN: 9781265977061
Chapter: Chapter 55 - "Alterations in Kidney Function"
Section: "Oliguria and Anuria" (Block 5, lines 2493-2502)
Key text (verbatim):
"Oliguria refers to a 24-h urine output <400 mL, and anuria is the complete absence of urine formation (<100 mL). Anuria can be caused by complete bilateral urinary tract obstruction; a vascular catastrophe (dissection or arterial occlusion); renal vein thrombosis; acute cast nephropathy in myeloma; renal cortical necrosis; severe ATN; severe rapidly progressive glomerulonephritis; combined therapy with NSAIDs, ACE inhibitors, and/or ARBs; and hypovolemic, cardiogenic, or septic shock. Oliguria is never normal, since at least 400 mL of maximally concentrated urine must be produced to excrete the obligate daily osmolar load. Nonoliguria refers to urine output >400 mL/d in patients with acute or chronic azotemia. With nonoliguric ATN, disturbances of potassium and hydrogen balance are less severe than in oliguric patients, and recovery to normal renal function is usually more rapid."
Summary - Causes of Anuria (Mnemonic Aid)
| Category | Key Examples |
|---|---|
| Pre-renal | Shock (hypovolemic, cardiogenic, septic), HRS |
| Renal - Vascular | Renal artery occlusion, renal vein thrombosis, HUS/TTP, malignant HTN |
| Renal - Glomerular | Severe RPGN, crescentic GN, ANCA vasculitis |
| Renal - Tubular | Severe ATN (ischemic/nephrotoxic), renal cortical necrosis, myeloma cast nephropathy, crush syndrome |
| Renal - Drug | NSAIDs + ACE-I + ARB combination |
| Post-renal | Bilateral calculi, bilateral ureteric ligation, massive BPH, pelvic malignancy |
Generate a diagnostic flowchart (PDF) for anuria workup: pre/renal/post
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Page 1 - Overview Diagnostic Flowchart
- Step-by-step decision flow from "patient presents with anuria" through bladder catheterisation, FENa assessment, renal ultrasound, and final categorisation into Pre-Renal / Intrinsic Renal / Post-Renal
- Color-coded cause boxes at the bottom (green = pre-renal, purple = intrinsic, red = post-renal)
Page 2 - Detailed Management by Category (3 columns)
- Each column covers: Diagnosis, Investigations, Management, and RRT indications
- Includes the KDIGO Stage 3 anuria criterion (≥12 h) and the AEIOU dialysis indications
Page 3 - Urine Indices Table + Quick Reference
- Side-by-side comparison of FENa, urine Na, osmolality, sediment by category
- Full KDIGO staging table with UO criteria
- 17-point emergency checklist for anuria workup
All references cite Harrison's 22nd Ed. (Ch. 55), Comprehensive Clinical Nephrology 7th Ed., Goldman-Cecil Medicine, and KDIGO 2012 guidelines.
Anuria Diagnostic Flowchart
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