Write a short note on the clinical assessment of kidney disease.

The Four Questions

A structured approach to any patient with suspected renal disease answers four questions in order:

1. Is the disease ACUTE or CHRONIC?

2. Where is the lesion — pre-renal, glomerular, tubulointerstitial, vascular or post-renal?

3. How severe is it — and are there immediate threats to life?

4. What is the underlying cause?

Acute or Chronic?

Remember two exceptions: kidneys are normal or enlarged in chronic disease due to diabetic nephropathy, amyloidosis, polycystic disease, myeloma or HIV nephropathy; and acute-on-chronic disease is common — a patient may have both.

History

• Urinary symptoms: oliguria, anuria, polyuria, nocturia (an early sign of impaired concentrating ability), frequency, dysuria, hesitancy and poor stream (obstruction), frothy urine (proteinuria), haematuria and its timing and colour.
• Systemic symptoms: oedema, breathlessness, fatigue, anorexia, nausea, pruritus, weight loss, fever, rash, arthralgia, haemoptysis.
• Past history: diabetes and its duration, hypertension, recurrent UTI or childhood enuresis, stones, prostatic symptoms, gout, recent infection (sore throat, skin sepsis, diarrhoea), pregnancy complications, autoimmune disease.
• DRUG HISTORY — critical: NSAIDs and analgesics (including long-term over-the-counter use), ACE inhibitors and ARBs, aminoglycosides, contrast exposure, chemotherapy, proton pump inhibitors, lithium, and traditional, ayurvedic and herbal preparations, which may contain heavy metals or aristolochic acid and are a genuine and under-recognised cause of interstitial nephritis in India.
• Family history: polycystic kidney disease, Alport syndrome (with deafness), hereditary nephritis, and consanguinity.
• Occupational and environmental: heavy metal exposure, agrochemicals, heat stress (relevant to CKD of unknown aetiology in agricultural communities).

Examination

• General: anaemia, uraemic sallow pigmentation, scratch marks, bruising, uraemic fetor, oedema (periorbital and dependent), nutritional status.
• BLOOD PRESSURE — in every patient, both a cause and a consequence of renal disease; postural measurement to assess volume status.
• Volume status — JVP, skin turgor, mucous membranes, capillary refill, lung bases, sacral and pedal oedema, daily weight.
• Abdomen: ballotable kidneys (polycystic disease, hydronephrosis, tumour), palpable bladder (obstruction — never omit this), renal bruit (renal artery stenosis), hepatomegaly.
• Rectal examination for prostatic enlargement in men with obstructive symptoms.
• Fundoscopy — diabetic or hypertensive retinopathy; retinopathy strongly supports diabetic nephropathy as the cause of proteinuria.
• Systemic clues: rash (vasculitis, SLE), joints, nasal crusting and saddle nose (GPA), hearing (Alport), neuropathy, pericardial rub (uraemic pericarditis — an indication for dialysis), asterixis.

Investigations

Urine — the most informative and most neglected investigation:

• Dipstick: protein, blood, leucocytes, nitrites, glucose, pH.
• MICROSCOPY OF FRESH URINE — "the renal biopsy of the poor":

• Quantify protein: urine protein:creatinine or albumin:creatinine ratio.
• Culture where infection is suspected; three early-morning samples for AFB and CBNAAT in sterile pyuria.

Blood:

• Creatinine with eGFR, urea, electrolytes, bicarbonate; cystatin C where muscle mass is atypical.
• CBC (anaemia), calcium, phosphate, PTH, alkaline phosphatase, vitamin D, uric acid, albumin, glucose and HbA1c, lipids.
• Immunological panel where indicated: ANA, anti-dsDNA, complement C3/C4, ANCA, anti-GBM, immunoglobulins, cryoglobulins, hepatitis B and C, HIV, ASO.
• Serum and urine protein electrophoresis with immunofixation and serum free light chains — essential in anyone over 50 with unexplained renal impairment, since myeloma is a classic missed diagnosis.

Imaging:

• ULTRASOUND KIDNEYS AND BLADDER — the essential first imaging test in every patient: kidney size, echogenicity, corticomedullary differentiation, hydronephrosis (obstruction), cysts, stones, and post-void residual volume.
• Doppler for renal artery stenosis and renal vein thrombosis.
• CT (non-contrast for stones); avoid contrast where possible, and hydrate if unavoidable. Avoid gadolinium in advanced CKD because of nephrogenic systemic fibrosis.
• Radionuclide scans for differential function and obstruction; MCUG and DMSA in children.

Renal Biopsy:

• Indications: unexplained AKI, nephrotic syndrome in adults, glomerulonephritis, systemic disease with renal involvement, unexplained proteinuria or haematuria with impaired function, and transplant dysfunction.
• Contraindications: bleeding diathesis or uncorrected coagulopathy, uncontrolled hypertension, single kidney (relative), small shrunken kidneys, active infection, and an uncooperative patient.
• Complications: haematuria, perinephric haematoma, arteriovenous fistula, and rarely nephrectomy or death — so it must be justified by a clear question that will change management.