Renal disease presents as:
1 Asymptomatic disease
• Non-visible haematuria: (NVH, microscopic haematuria.) Detected on urine dipstick on repeated testing. Most is not due to renal disease and urological investigation is fi rst-line for all those aged >40 years.
• Asymptomatic proteinuria: Normal renal protein excretion is less than 150mg/24 hours (non-pregnant). Quantifi cation by 24h urine collection is unreliable and rarely used in clinical practice. A spot urinary protein to creatinine ratio (P:CR) >15mg/mmol or urinary albumin to creatinine ratio (A:CR) >2.5(or 3.5mg/mmol may signify either glomerular (common) or tubular (rare)pathology.
• Abnormal renal function (GFR): The glomerular fi ltration rate (GFR) is a measure of how much blood the kidneys are cleaning per minute. Direct measurement is invasive and time-consuming. Estimations derived from equations based on serum creatinine are widely used to give an eGFR . Errors in eGFR are caused by nonsteady-state conditions, conditions which alter serum creatinine (diet, muscle mass), and eGFR is less accurate at higher levels of GFR.
eGFR is therefore only part of the assessment of renal function.
• High blood pressure: A renal aetiology should be excluded if hypertension occurs with any indicators of renal disease: haematuria, proteinuria, eGFR.
• Electrolyte abnormalities: Disorders of sodium, potassium, and acid–base balance may be due to underlying renal disease.
2 With renal tract symptoms
• Urinary symptoms: Dysuria is a sensation of discomfort with micturition and may be accompanied by urgency, frequency, and nocturia. UTI is the primary diff erential. Consider prostatic aetiology if there is diffi culty initiating voiding, poor stream and dribbling. Oliguria (<400mL/24 hours or <0.5mL/kg/hour) and anuria should trigger assessment and investigation for acute kidney injury (AKI) . Poly uria is the voiding of abnormally high volumes of urine, usually from high fl uid intake. Consider also DM, diabetes insipidus , hypercalcaemia, renal medullary disorders (causing impaired concentra- tion of urine).
• Loin pain: Ureteric colic is severe and radiates anteriorly and to the groin. It is caused by a renal stone, clot, or a sloughed papilla. For pain confi ned to the loin consider pyelonephritis, renal cyst pathology, and renal infarct.
• Visible haematuria: (VH, macroscopic.) Urological investigation is required to exclude renal tract malignancy. Nephrological causes include polycystic kidney disease and glomerular disease (IgA, antiglomerular basement membrane (anti-GBM) disease , Alport syndrome.
• Nephrotic syndrome: Proteinuria >3g/24 hours (=P:CR >300mg/mmol) with hypoalbuminaemia (<30g/L) and peripheral oedema. Renal biopsy is usually indicated in adults .
• Symptomatic chronic kidney disease: Dyspnoea, anorexia, weight loss, pruritus, bone pain, sexual dysfunction, cognitive decline .
3 A systemic disorder with renal involvement
• DM
• Metabolic: Sickle cell disease , tuberous sclerosis , Fabry disease
, cystinosis .
• Auto-immune: ANCA-associated vasculitis , SLE, Henoch Schonlein purpura , systemic sclerosis , sarcoid , Sjögren’s syndrome .
• Infection: Sepsis is a common cause of AKI. Specifi c renal involvement may occur with TB ), malaria, chronic hepatitis , HIV .
• Malignancy: Obstruction, hypercalcaemia, direct toxicity, eg myeloma .
• Pregnancy: Pre-eclampsia, obstruction.
• Drugs used in systemic disorders: NSAIDS, ACE-i, ARB, aminoglycosides, chemotherapy.