Kidney and urinary tract disease

10 Kidney and urinary tract disease




Approach to the Patient


The history should include a history of prior tests of renal function, previous urinary dipstick and BP recordings, and an obstetric (e.g. hypertension during pregnancy) and family history (e.g. inherited disorders).



Clinical presentations







Examination of the urine




Proteinuria. Normally the amount of protein in the urine should not exceed 150 mg/L, of which albumin should be < 20 mg/L. Significant proteinuria is a sign of glomerular disease, and usually consists predominantly of albumin (Bence Jones protein, as found in multiple myeloma, is an exception). ‘Nephrotic range proteinuria’ is a loose term, usually implying > 3 g/day of urine albumin loss and usually sufficient to cause hypoalbuminaemia. The urine dipstick is a sensitive marker of proteinuria. Quantification can be performed by measurement of:




The urine dipstick is a sensitive detector of haem and if the dipstick is negative, blood is most unlikely to be present in the urine. If haematuria is found, then infection should be excluded (by sending a specimen of urine for culture) and the dipstick should then be repeated. Urine microscopy is useful to:






Evaluation of Renal Function



Glomerular disease


Plasma is filtered by the glomerulus. Failing glomeruli filter progressively less of the plasma, leading to a fall in glomerular filtration rate (GFR). Filtered uraemic toxins accumulate and lead to the uraemic syndrome. Large molecules (such as proteins) and cells are not normally filtered, but may appear in the urine as proteinuria or haematuria if the glomerular filter is injured (as occurs in glomerulonephritis).



Measuring GFR


GFR is defined as the volume of plasma theoretically filtered in a unit of time (measured in mL/min). Normal GFR is 60–120 mL/min. Clinical estimation of GFR is by:







Imaging in renal disease


Many renal disorders are associated with normal imaging. The choice of imaging depends on the clinical presentation and on the information required.












Urinary Tract Infection (UTI)


Half of all women will have at least one UTI in their lifetime. Serious morbidity is unusual. Most patients have no anatomical abnormality of the renal tract and do not require further investigation, but patients with recurrent infections should be investigated. Renal stones, incomplete bladder emptying, duplex ureters, tumour or any other cause of disturbed urinary flow or stasis are predisposing factors, as are increasing age (loss of oestrogen in vaginal secretions) and recent or frequent intercourse. UTIs in men are unusual, and should always be investigated with imaging to look for abnormalities of urinary flow.








Glomerular Disease









Management of glomerular disease: general principles



Salt and water balance. Accurate assessment of fluid balance is necessary (p. 368), as in severe nephrotic syndrome there may be intravascular depletion despite expansion of the extracellular compartment. Hypovolaemia should be corrected with oral or IV fluids. Volume expansion should be managed with salt and water restriction, with or without diuretics. High doses of loop diuretics are often required to establish and maintain a diuresis, e.g. furosemide 40–250 mg twice daily.




Dialysis. This is required if renal impairment is severe. For indications for dialysis see p. 357. With definitive treatment and renal recovery, dialysis is discontinued after a period of time.





General principles for immunosuppressive treatment











Specific glomerular diseases and their management



Minimal change disease


Minimal change disease presents as the nephrotic syndrome, often of sudden onset with no haematuria. It is most common in children (boys > girls) and accounts for > 95% of all cases of nephrotic syndrome in children, although it can occur at any age and accounts for up to 25% of all nephrotic syndrome in adults.








Focal segmental glomerulosclerosis (FSGS)


FSGS usually presents with the nephrotic syndrome, often with microscopic haematuria. Hypertension and/or progressive renal impairment are often present.


Primary FSGS is of unknown cause. A circulating permeability factor with serine protease activity has been implicated (the disease may recur after transplantation, often immediately). A renal biopsy is required to make the diagnosis, determine therapy and indicate prognosis. Segmental scleroses in affected glomeruli are seen, with other glomeruli looking normal on light microscopy. C3 and IgM may be present on immunofluorescence in affected segments. Mesangial hypercellularity may be present. Interstitial fibrosis and focal tubal atrophy are common. On EM, affected glomeruli show capillary obliteration with hyaline deposits and lipids. Patchy foot process effacement is present, even on ‘normal’-looking glomeruli. Five histological types are described by light microscopy:






Management. Mild to modest proteinuria should be managed with good BP control (ACE inhibitors), a statin and follow-up (Box 10.1). Overt nephrotic syndrome and/or progressive renal impairment (drop in eGFR of > 15% in 1 year or > 10% in 2 successive years) are risk factors for progression and indications for immunosuppression. Prednisolone 0.5–2 mg/kg/day should be continued for up to 6 months before steroid resistance is diagnosed. Commonly this is the case, and other disease-modifying drugs are required. Ciclosporin aiming for trough level 150–300 ng/mL may be effective, but relapse may occur when it is discontinued. Cyclophosphamide 1–1.5 mg/kg/day with high-dose prednisolone for 3–6 months, followed by maintenance treatment with prednisolone and azathioprine, may reduce proteinuria and slow progression, especially if there is mesangial hypercellularity and tip lesions. Chlorambucil has also been used with some success. Despite treatment, 50% progress to end-stage kidney disease within 10 years of diagnosis. HIVAN is managed with anti-retroviral therapy. Renal function may stabilize or improve.



Membranous glomerulonephritis


Membranous glomerulonephritis presents with nephrotic syndrome or asymptomatic proteinuria with or without renal impairment, microscopic haematuria and hypertension. It usually affects adults, mainly men. Spontaneous remission can occur. Specific treatment should be reserved for those with overt nephrotic syndrome and/or progressive renal impairment. Older age at presentation, male sex and heavy proteinuria are risk factors for progression.





Apr 2, 2017 | Posted by in GENERAL SURGERY | Comments Off on Kidney and urinary tract disease

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