Chronic kidney disease for the primary care clinician

An epidemic of chronic kidney disease (CKD) is being experienced in South Africa. This is driven by a heavy burden of infections, non-communicable diseases, pregnancy-related diseases and injuries. The serious long-term complications of CKD include end-stage renal disease, heart disease and stroke. Competing priorities such as the high burden of HIV, tuberculosis and other infections, unemployment and poverty result in serious constraints to providing comprehensive renal care, especially in the public healthcare sector. The prevention and early detection of CKD by primary care practitioners is therefore of utmost importance. Annual screening is recommended for patients at high risk of developing CKD. This involves checking blood pressure, urine dipstick testing for albuminuria or proteinuria and estimating the glomerular filtration rate from serum creatinine concentrations. In patients with established CKD, renoprotective measures are indicated to arrest or slow down the loss of renal function. These patients are at high risk of cardiovascular disease and close attention should be paid to optimally managing their risk factors.

Encapsulating peritoneal sclerosis presenting with haemorrhagic ascites after transfer from peritoneal dialysis to haemodialysis

A patient with end-stage kidney disease due to chronic glomerulonephritis was initiated on continuous ambulatoryperitoneal dialysis. After three years he was transferred to haemodialysis following recurrent episodes of peritonitis. After the commencement of haemodialysis the patient developed progressive abdominal distension; paracentesisrevealed bloody ascites. Radiographic imaging revealed features of small bowel obstruction with bowel loops matted tothe posterior abdominal wall. A diagnosis of encapsulating peritoneal sclerosis was made. Treatment with prednisonewas initiated but the patients condition steadily worsened and he demised a year later due to severe malnutrition andsepsis.

Association between periodontitis and systemic inflammation in patients with end-stage renal disease

Patients with end-stage renal disease (ESRD) experience a significantly increased rate of atherosclerotic complications. Inflammation plays a central role in the pathogenesis of these complications and C-reactive protein (CRP) has been found to be predictive of all-cause and cardiovascular mortality. Many patients have elevated CRP levels without an apparent infection. Periodontal diseases in the general population have been associated with both an increased prevalence of atherosclerotic complications and an elevation in serum CRP values. This study examined the association between periodontal disease and elevated CRP in patients with ESRD on chronic dialysis.

METHODS

Eighty patients on chronic dialysis were included in the study. Demographic information, medical history and CRP levels were recorded. Periodontal examination was carried out by a single calibrated examiner and included gingival index (GI), bleeding on probing (BoP), probing depths (PD) and clinical attachment loss (CAL). These measurements were recorded in relation to the Ramfjord teeth. The presence in any one sextant of PD > or =4 mm or clinical loss of attachment > or =3 mm was diagnosed as periodontitis.

RESULTS

Mean age of subjects was 50.3 +/- 9.06 years with a median time on dialysis of 24 months. 57.5% (n=46) of subjects were diagnosed as having periodontitis; of these 52.2% had CRP levels >10 mg/l. Of the 34 subjects with healthy periodontium, only 10 (29.4%) had elevated CRP levels. The serum CRP levels between these two groups were significantly different (p = 0.004).

CONCLUSION

The results of the study showed significantly elevated levels of CRP in ESRD patients with periodontitis. Periodontal diseases may be an overlooked source of inflammation in ESRD patients.

Antenatal Bartter's syndrome: why is this not a lethal condition?

There are four themes in this teaching exercise for Professor McCance. The first challenge was to explain how a premature infant with Bartter's syndrome could survive despite having such a severe degree of renal salt wasting. Second, the medical team wanted to know why there was such a dramatic decrease in the natriuresis in response to therapy, despite the presence of a permanent molecular defect that affected the loop of Henle. Third, Professor McCance was asked why this patient seemed to have a second rare disease, AQP2 deficiency type of nephrogenic diabetes insipidus. The fourth challenge was to develop a diagnostic test to help the parents of this baby titrate the dose of indomethacin to ensure an effective dose while minimizing the likelihood of developing nephrotoxicity. The missing links in this interesting story emerge during a discussion between the medical team and its mentor.

Uncovering the basis of a severe degree of acidemia in a patient with diabetic ketoacidosis

In this teaching exercise, the goal is to demonstrate how an application of principles of physiology can reveal the basis for a severe degree of acidaemia (pH 6.81, bicarbonate <3 mmol/l (P(HCO(3))), PCO(2) 8 mmHg), why it was tolerated for a long period of time, and the issues for its therapy in an 8-year-old female with diabetic ketoacidosis. The relatively low value for the anion gap in plasma (19 mEq/l) suggested that its cause was both a direct and an indirect loss of NaHCO(3). Professor McCance suggested that ileus due to hypokalaemia might cause this direct loss of NaHCO(3), and that an excessive excretion of ketoacid anions without NH(4)(+) in the urine accounted for the indirect loss of NaHCO(3). In addition, he suspected that another factor also contributing to the severity of the acidaemia was a low input of alkali. He was also able to explain why there was a 16-h delay before there was a rise in the P(HCO(3)) once therapy began. The missing links in this interesting story, including a possible basis for the hypokalaemia, emerge during the discussion between the medical team and Professor McCance.

A hyperglycaemic hyperosmolar state in a young child: diagnostic insights from a quantitative analysis

This teaching exercise demonstrates how the application of principles of physiology can identify the cause of a severe degree of hyperglycaemia (plasma glucose concentration 80 mmol/l) in a very young patient with newly diagnosed diabetes mellitus, determine whether the patient has diabetic ketoacidosis, and highlight the potential risks for this patient on admission and during initial therapy. A consultation with Professor McCance was sought to determine whether this patient had an unusual degree of 'insulin resistance'. There were also uncertainties regarding the acid-base diagnosis. The patient did not appear to have an important degree of metabolic acidosis as judged from his pH of 7.39 and plasma bicarbonate concentration of 20 mmol/l in arterial blood; hence the diagnostic impression was that he had a hyperglycaemic hyperosmolar state. However, his plasma anion gap was significantly elevated, and remained so for 60 h, despite the administration of insulin. Issues in management concerning the basis for this severe degree of hyperglycaemia and how to minimize the risk of developing cerebral oedema are addressed. The missing links in this interesting story emerge during a discussion between the medical team and their mentor, Professor McCance.

The patient with a severe degree of metabolic acidosis: a deductive analysis

This teaching exercise demonstrates how principles of physiology might help in identifying the cause of a particularly severe case of metabolic acidosis and making appropriate decisions about therapy. The patient's plasma pH was 7.00 and their plasma bicarbonate concentration was 2 mmol/l. Because the time course of the patient's illness was believed to be <24 h, this suggested that a large quantity of acid had been added to the body in this short time period, but the medical team managing the case could not identify any acid that could have been produced rapidly by endogenous processes, or was ingested by the patient. Moreover, there was a question about how such a very low arterial PCO(2) (8 mmHg) could be sustained. Even once the diagnosis was made, there were issues to resolve concerning therapy. These included questions about how much sodium bicarbonate to administer, and what dangers might arise during this therapy. The missing links in this interesting story emerge during a discussion between the medical team and their imaginary mentor, Professor McCance.

Unusual causes of hypokalaemia and paralysis

We demonstrate how the application of physiological principles may help to identify unusual causes of a very low plasma potassium (K+) concentration (P(K)) and paralysis. In the two patients described, the short time course of the illness suggested that there was an acute shift of K+ into cells. The combination of a low rate of excretion of K+, the absence of a metabolic acid-base disorder, and the fact that the clinical findings occurred very soon after a large intake of carbohydrate supported this impression. Surprisingly, the P(K) remained low for many hours after these stimuli to shift K+ into cells had abated. The missing link in this story was eventually provided by the attending medical team with the help of their mentor, Professor McCance.

Acute and fatal hyponatraemia after resection of a craniopharyngioma: a preventable tragedy

Central diabetes insipidus developed for the first time in a 14-year-old female during the resection of a craniopharyngioma. The water diuresis persisted until a vasopressin analogue (dDAVP) was given. Professor McCance was asked to explain why hypernatraemia developed, to anticipate dangers that might develop in the salt and water area with therapy, and to provide insights into why this patient died, due to the subsequent development of hyponatraemia that caused a lethal rise in intracranial pressure. The team specifically wanted Professor McCance's opinions as to why a PNa of 124 mmol/l was uniquely dangerous for this patient, and this was a particularly challenging conundrum. Nevertheless, with the aid of a mini-experiment, a careful chart review, and creative thinking, he was able to offer a novel solution, and to suggest ways to prevent its occurrence in other patients.

An approach to the patient with severe hypokalaemia: the potassium quiz

The objective of this teaching session with Professor McCance is to develop an approach to the management of patients with a very low plasma potassium (K(+)) concentration (P(K)). The session begins with a quiz based on six recent medical consultations for a P(K) < 2 mmol/l. Professor McCance outlined how he would proceed with his diagnosis and therapy, using the synopsis that described each patient. This approach was then applied to a new patient, a 69-year-old woman who had a large volume of dependent oedema and developed a severe degree of weakness and hypokalaemia during more aggressive diuretic therapy that included a K(+)-sparing diuretic. The initial challenge for Professor McCance was to deduce why the K(+)-sparing diuretic was not effective in this patient. He also needed to explain why the P(K) was so low on admission.

Recurrent uric acid stones

A 46-year-old female had a history of recurrent uric acid stone formation, but the reason why uric acid precipitated in her urine was not obvious, because the rate of urate excretion was not high, urine volume was not low, and the pH in her 24-h urine was not low enough. In his discussion of the case, Professor McCance provided new insights into the pathophysiology of uric acid stone formation. He illustrated that measuring the pH in a 24-h urine might obscure the fact that the urine pH was low enough to cause uric acid to precipitate during most of the day. Because he found a low rate of excretion of NH(4)(+) relative to that of sulphate anions, as well as a high rate of citrate excretion, he speculated that the low urine pH would be due to a more alkaline pH in proximal convoluted tubule cells. He went on to suspect that there was a problem in our understanding of the function of renal medullary NH(3) shunt pathway, and he suggested that its major function might be to ensure a urine pH close to 6.0 throughout the day, to minimize the likelihood of forming uric acid kidney stones.

Acidosis in a patient with cholera: a need to redefine concepts

A patient presented with cholera and a severe degree of ECF volume contraction. Despite large losses of bicarbonate (HCO3-)-containing diarrhoeal fluid, laboratory acid-base values were remarkably close to normal. A detailed analysis emphasizing principles of physiology and a quantitative approach provided new insights and eventually better definitions of metabolic and respiratory acidosis. A shift in focus from HCO3- concentration to HCO3- content in the extracellular fluid (ECF) compartment revealed the presence of metabolic acidosis. Central to this analysis was an emphasis on the haematocrit to enable a more accurate estimate of the degree of ECF volume contraction. The latter also revealed 'contraction' metabolic alkalosis, which masked the underlying metabolic acidosis. The presence of a respiratory acidosis of the tissue type was evident from the raised venous PCO2, which was not surprising once the magnitude of the ECF contraction had been appreciated. 'Bad buffering', as defined by Professor McCance, was the immediate danger and prompted swift action to restore an effective circulation. The haematocrit and the venous PCO2 also contribute valuable information to monitor the response to therapy. Nevertheless, there were still dangers to be discovered when an in-depth analysis suggested that the administration of isotonic saline would introduce an unanticipated danger for the patient.

An unusual cause for ketoacidosis

A 22-year-old male developed a severe degree of metabolic acidosis (plasma pH 7.20, bicarbonate 8 mmol/l), with a large increase in the plasma anion gap (26 mEq/l). Ketoacidosis was suspected because of the odour of acetone on his breath and a positive qualitative test for acetone in plasma (to a 1:4 dilution). Later, his plasma beta-hydroxybutyrate concentration was found to be 4.5 mmol/l. After receiving an infusion of 1 l of half-isotonic saline and 1 l of 5% dextrose in water over 24 h, as well as curtailing his large oral intake of sweetened beverages, all blood tests became normal. Diabetic ketoacidosis, alcoholic ketoacidosis, starvation ketosis and hypoglycaemic ketoacidosis were all ruled out, and his toxin screen was negative for salicylates. Finding another possible cause for ketoacidosis became the focus of this case.

Anorexia nervosa and chronic renal insufficiency: a prescription for disaster

Our imaginary consultant, Professor McCance, is asked to explain the basis for four major acute electrolyte abnormalities in a young woman with long-standing anorexia nervosa. She has a severe degree of hypokalaemia (2.0 mmol/l) with renal potassium wasting, a contracted extracellular fluid volume with renal NaCl wasting, hyponatraemia (118 mmol/l) while excreting hypoosmolar urine, and metabolic acidosis with a normal plasma anion gap (pH 7.20, bicarbonate 9 mmol/l). McCance begins his discussion by considering the basis for hypokalaemia, as this electrolyte disorder is potentially life-threatening. Its pathophysiology is linked to the other major findings, using principles of integrative physiology together with a deductive and quantitative analysis. Nevertheless, to reach his final diagnosis, he requires information about newer molecular discoveries. Not only is he able to suggest a likely diagnosis, but he also devises a novel long-term plan for therapy.

Osmotic demyelination syndrome: a potentially avoidable disaster

Osmotic demyelination of the brain (ODS) is a dreaded complication that typically occurs several days after aggressive therapy for chronic hyponatraemia, but is eminently avoidable. In this teaching exercise, Professor McCance, an imaginary consultant, is asked to explain how he would have treated a 28-year-old female who had hyperkalaemia, hypoglycaemia, hypotension and hyponatraemia (118 mM) to prevent the development of ODS. He begins with a review of the physiology, including his own landmark work on chronic hyponatraemia associated with a contracted extracellular fluid volume. Adding quantitative analysis, the cause of the excessive rise in plasma sodium concentration is revealed, and a better plan for therapy is proposed.

An integrative physiological approach to polyuria and hyponatraemia: a 'double-take' on the diagnosis and therapy in a patient with schizophrenia

A patient with a history of schizophrenia was brought to the emergency department with extensive self-inflicted soft tissue injuries. Primary polydipsia was evident on admission, because he had a maximally dilute urine, a urine flow rate of 10 ml/min, and hyponatraemia (100 mmol/l). During an imaginary consultation with Professor McCance in which he applied basic principles of integrative physiology and a deductive analysis in quantitative terms, other reasons for the polyuric state were considered. Moreover, based on the very low value for the concentration of urea in plasma (< 0.7 mmol/l, BUN 1 mg /dl), the goals of therapy to prevent osmotic demyelination became evident. Applying this simple approach, a more comprehensive and accurate differential diagnosis, and a plan for therapy to avoid serious complications was compiled.

Hypokalaemia and paralysis

A patient with a severe degree of hypokalaemia (1.8 mmol/l) and paralysis was brought to the emergency department. Hypokalaemic periodic paralysis was an unlikely diagnosis, because an acid-base disorder (metabolic alkalosis) and a high rate of potassium (K(+)) excretion were present. During an imaginary consultation with Professor McCance, the combination of emphasis on principles of integrative physiology, a deductive analysis, common sense, and clinical skills led to an obvious diagnosis. Nevertheless, a surprise was in store, because renal K(+) wasting persisted for almost 2 weeks after removal of the causative agent. Possible explanations for the continued kaliuresis, as well as therapeutic strategies to avoid potential complications, were considered. This case illustrates the value of applying principles of physiology in a quantitative fashion at the bedside.

Severe hypokalaemia in a Chinese male

A 34-year-old Chinese man developed acute, severe, generalized muscle weakness while mountain climbing. In the Emergency Department that morning, the most striking abnormalities were flaccid paralysis of both upper and lower limbs and a plasma potassium (K+) concentration (P(K)) of 1.7 mmol/l. To explain the basis for this constellation of findings, an imaginary consultation was sought with Professor McCance, the legendary integrative physiologist. Using both a deductive and a quantitative analysis, he illustrated that a simple story of an acute shift of K+ into cells was not sufficient to explain the patient's hypokalaemia. The clue he used to suspect a large total body deficit of K+ was a higher than expected rate of K(+) excretion on the initial spot urine (higher than expected ratio of K+: creatinine in the urine). This interpretation was supported by the fact that the patient needed a large supplement of K(+) to raise his P(K) to just under 3 mmol/l. It was only after more detailed studies based on urine chemistry that an accurate diagnosis and effective treatment could be instituted. The final question was why one of the hallmarks of the diagnosis of hyperaldosteronism (hypertension) was absent, yet hypokalaemia was so severe.

Acute hyponatraemia and 'ecstasy': insights from a quantitative and integrative analysis

A 20-year-old woman attended a 'rave party' where she took the drug 3,4-methylenedioxymethamphetamine (MDMA, 'ecstasy'). She had used this drug previously without serious adverse effects. On this occasion, while both she and her friends drank a large quantity of water, only she became seriously ill. The initial manifestation was an altered sensorium; several hours later she had a grand mal seizure. In the Emergency Department, the most striking features were the severe degree of hyponatraemia (112 mmol/l) and cerebral oedema. To explain the basis for this life-threatening clinical presentation, an imaginary consultation was sought with Professor McCance. Using both a deductive and a quantitative analysis that involved several medical subspecialties, he illustrated that a simple story of water ingestion and vasopressin release was not sufficient to explain her hyponatraemia. It was only after events in her gastrointestinal tract were analysed that a plausible hypothesis could be constructed.

Hyponatraemia and hyperglycaemia during laproscopic surgery

The aim of this masterclass is to develop a rational plan of therapy to deal with a severe degree of hyponatraemia (90 mmol/l) and hyperglycaemia (100 mmol/l) that occurred 100 min after the start of laproscopic surgery in a young woman. The lavage fluid used in this procedure was 10% dextrose.H(2)O in water (505 mmol glucose/l). To focus attention on specific issues, three questions are posed to the reader, as they were to a panel of 59 modern-day experts. Two imaginary consultants from the past were asked the same (and additional) questions. Their responses were restricted to knowledge available before the molecular era, to show the power of integrative physiology at the bedside. An analysis of intracellular events was helpful in answering the first question: 'Is an infusion of hypertonic saline required to treat her acute hyponatremia?' Similarly, a quantitative analysis of changes in the composition of the extracellular fluid compartment was helpful in answering the second question: 'Is an infusion of isotonic saline required to treat her hypotension?' A metabolic analysis was used to answer the third question, 'Should insulin be administered?'

Severe degree of hyperglycaemia: insights from integrative physiology

We illustrate how the application of principles of integrative physiology at the bedside can reveal novel insights that have been largely overlooked to this day. In this didactic exercise, modern-day physicians seek an imaginary medical consultation with Professor Sir Hans Krebs because of an unusual finding in his area of expertise: a very severe degree of hyperglycaemia. Although Professor Krebs is restricted to data prior to World War II, this does not prevent him from making novel discoveries. First, he illustrates how an occult factor, rapid absorption of glucose from the intestinal tract, was a critical feature in explaining the basis of the severe degree of hyperglycaemia without obvious ketoacidosis in a 16-year-old patient with type 1 diabetes mellitus in poor control. Second, by examining simple principles of renal and gastrointestinal physiology in a quantitative fashion, Professor Krebs speculates as to how cerebral oedema might occur before therapy in a patient with a severe degree of hyperglycaemia. We hope that readers and educators will appreciate the value of applying principles of integrative physiology in a quantitative fashion at the bedside.

The approach to a patient with acute polyuria and hypernatremia: a need for the physiology of McCance at the bedside

We present a case to illustrate the importance of emphasizing elementary physiology to deduce the basis for the acute onset of polyuria and hypernatremia. An imaginary consultation with Professor McCance is utilized to illustrate how a clinician-physiologist would have explained why these abnormalities developed and how they should have been treated. His approach began with a consideration of the most impressive abnormality. His analysis relied heavily on deductions and the anticipation of the expected responses to a stimulus in quantitative terms. The goals of therapy became evident after he performed mass balance calculations. Professor McCance would not understand why modern clinicians abandoned this form of analysis.