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Download K4.Chronic renal failure for doctors
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CHRONIC RENAL FAILURE IN PRIMARY HEALTH CARE for doctors Chronic renal failure seems to have a higher incidence in poorer communities in the tropics. There is a possible role for recurrent skin infections by streptococci even though traditionally these infections were thought not to cause permanent renal damage. Dehydration in hot climates and inappropriate use of traditional and Western nephrotoxic drugs may also contribute. In older people CRF is caused by the same risk factors that cause ischemic heart disease and so CRF is becoming more common in older people for the same reason that IHD is becoming more common in India. Is there a screening test? Proteinuria by dipstick testing is not adequately specific for chronic renal disease, and does not lead to proper effective interventions. In diabetic people who are at high risk of renal disease, the detection of microalbuminuria may lead to cost effective interventions using ACE inhibitors. Unfortunately standard dipsticks are not sensitive enough to detect microalbuminuria. It needs measurement of urine albumin creatinine ratios. The cost of this measurement is high and if it’s high costs make a poor person abandon cost-effective treatments in diabetes such as BP control and blood glucose control, then ACR measurement is counterproductive. Serum creatinine is not sensitive enough to detect early kidney failure for screening. More than 50% glomerular function is lost before serum creatinine increases. The reduced muscle bulk of Indian patients makes serum creatinine even less sensitive for screening. Nevertheless in those at risk of renal disease like diabetics and hypertensive people, yearly calculation of GFR using creatinine and weight (eGFR) may help if costs are not a problem. If costs are a problem, eGFR is not worthwhile because prevention of CRF needs primarily good control of BP more than anything else. By doing unnecessary tests you might prevent people from at least coming and taking BP tablets. The best choice for screening for CRF is BP measurement at every patient contact (opportunistic screening) or population screening. What are the symptoms? Remember that chronic renal failure may present suddenly because a recent even minor insult such as mild dehydration can unmask pre-existing asymptomatic CRF that occurred over a long time. This acute presentation after a minor illness is common in India where minor symptoms earlier could have been ignored. In such acute presentations of CRF, you must exclude acute renal failure without any pre-existing CRF. The only absolute way is through an ultrasound exam to assess renal size, a skill that is well within the scope of a family physician to learn and keep up to date. Other ways of presentation of CRF are tiredness or weakness dizziness breathlessness on effort swelling face or legs High BP on routine screening: Any person <40 years with incidental increase BP or those older with anaemia or proteinuria and high BP must have serum creatinine checked. Should you look for a cause? Ultrasound examination to rule out stones and obstruction is essential. Urine microscopy and if needed culture may reveal infection, which could suggest chronic pyelonephritis or reflux as a cause of CRF. More likely however infection complicates rather than causes CRF arising from other causes and may make it progress faster. Renal biopsy is very expensive and may tell you a prognosis but very rarely leads to treatment that will change out come. It should not be done routinely. Management of CRF in resource restricted situations is very difficult, but one need not be entirely negative. Simple cheap and careful management can keep many people fit for long periods. A crucial part of treatment is explaining the illness and objectives of treatment to family and patient. It will take time and repeated explanation, but you need to explain limitations of treatment, yet give hope that in some cases there is still useful life. Only then patients may cooperate with the treatment that has limited benefits. Patients need to be on the follow up register. The mainstay of treatment is 1. Avoid factors that cause CRF to progress fast: High BP: High BP is very serious in CRF and you must lower it if possible to systolic of 110 and diastolic 80 provided there is no major deterioration in CRF. If the person has diabetes and early CRF ACE inhibitors may help slow progression of CRF more than other drugs. Renal artery stenosis is a known contraindication to ACE inhibitors but is rare in poorer communities. Suspect renal artery stenosis only in those likely to have other risk factors of cardiovascular disease. If using ACEi in CRF recheck serum creatinine 4 days after starting ACE inhibitors. A greater than 15% rise of serum creatinine would indicate a need to stop ACE inhibitors. Its best to stop ACEi once CRF is severe so that eGFR is <30ml/h. Fat soluble beta blockers like propranolol and calcium channel blockers are first line drugs in those without diabetes or who have advanced CRF. Diuretics should be added if there is fluid overload, but must not allow dehydration to occur. Explain to family when diuretics need to be withheld (eg during diarrhoea). Control of severe hypertension will slow progression of CRF and may even lead to improvement in renal function. Stop dehydration! In hot climates, dehydration can rapidly make CRF worse. Patients with CRF must drink as much water as possible as long as swelling does not occur. This step is especially important during work in the sun. In late CRF vomiting is a problem that can rapidly hasten the end in late stages. It is not easy to treat, but metochlorpromide may help. Salt restriction: Those with high BP or oedema must restrict salt. Some patients without high BP or swelling need extra salt (salt losing nephropathy). Salt is permitted once BP is controlled to a level that allows BP to remain controlled or till swelling occurs. Diet: There is no need to restrict protein because poor families already have severe protein restriction and further restriction will cause serious malnutrition. Potassium restriction may be needed in some people especially those on ACE inhibitors if serum potassium is high. Avoid certain drugs: Be careful in choosing drugs in CRF! Major culprits are NSAIDS and tetracyclines, aminoglycosides. Know when to seek help Explanation should help those in CRF seek help earlier in minor illnesses. Your health workers need to know when to refer them. Write down clear guidelines for referral and treatment of simple illnesses in patient notes. Look for UTI; Protein leak in CRF makes infection likely. Some infections are silent. Use the dipstick test to screen for infection- if nitrites and leukocytes are positive infection is very likely. If only one of these is positive infection is possible. Untreated UTI makes CRF progress faster. 2. Manage complications Anaemia: in CRF anaemia can be due to multiple causes: Iron and folate deficiency can occur due to poor diet, iron deficiency due to gastritis and the anaemia of CRF due to erythropoietin deficiency. Measurement of iron, transferrin or ferritin to differentiate causes is not helpful because ferritin and transferrin levels are markedly affected by CRF itself. Blood film may show microcytic hypochromic anaemia, but the simplest intervention is preventive iron and folate supplement (eg macrofolin 1 tab daily or parenteral iron and oral folate if oral iron is not tolerated. If anaemia still occurs then it is likely due to erythropoietin deficiency. Erythropoietin injections have markedly improved quality of life in those with advanced CRF because anaemia can be very debilitating. The dose can be reduced to 4000U every 4 weeks and still produce significant rise in haemoglobin, but even this dose is simply expensive. Renal osteodystrophy: The current sad state of CRF management for those who are poor is such that most die long before renal osteodystrophy causes problems. Apart from addition of calcium to the diet, other interventions such as synthetic activated vitamin D analogues simply increase costs and may drive away patients from taking more sustainable and important interventions such as BP medications. Acidosis: People in CRF already need many medications. Routine addition of sodium or calcium bicarbonate markedly increases the number of tablets and is not useful. Acidosis in CRF is a late problem when prognosis is poor and when palliative care may be the best option. Cardiovascular disease: Many older CRF patients if they survive long develop cardiovascular (CVS) disease and in Western countries most die of CVS disease.. So reduce cardiovascular risk by stopping smoking and encouraging healthy diet and moderate physical activity. Lowering cholesterol with statin tablets like atorvastatin is expensive but may need to be considered if costs will not put people off from taking BP medications which are more important. It is important to be realistic. CRF is difficult to manage end stage without dialysis and erythropoietin. There comes a time when treatment needs to change from aggressive BP control etc, to palliative care and symptom control.