Acute kidney injury (AKI)

Acute kidney injury (AKI) can generally be considered as sudden reduction in kidney function occurring over hours to days, and is commonly but not always associated with a reduction in urine output. Its definition was based on rises in serum creatinine and reductions in urine output criteria. Its incidence, prevalence, and aetiology vary according to the country/region profile (low income, high income, tropical, etc.), age (children, adult, or elderly), and clinical setting (outpatients versus inpatient, hospital versus intensive care unit). The incidence of AKI is increasing in the hospital setting, and is more common with increasing age, male sex, pre-existing CKD, and comorbidity (congestive cardiac failure, diabetes, hypertension). The majority of cases result from multiple insults: dehydration, drugs in conjunction with inflammation and/or sepsis. AKI may have a spectrum of being an incidental finding with no signs or symptoms to a moderate to severe condition with increased morbidity and mortality due to accumulation of nitrogenous waste products and fluid–electrolyte disorders. The aetiologies of AKI are numerous and can broadly be classified as pre-renal, intrinsic renal, and post-renal (obstructive). A thorough evaluation of the patients with AKI for diagnosis and treatment are required. There are no specific treatments, but eliminating aetiological reasons and protection from further kidney function loss are crucial. A balanced haemodynamic management along with a balanced fluid–electrolyte replacement and arranging drug dosages are important. Various modes of renal replacement therapies may be used for treating severe cases.

Pregnancy and the kidney

Renal disease may occur de novo during pregnancy and pregnancy may occur in women with pre-existing renal disease. The chapters in this section consider the causes and implications of acute kidney injury that may occur during pregnancy and the likely outcomes of pregnancy in women with pre-existing chronic kidney disease, including the possible maternal and foetal complications of preterm delivery and pre-eclampsia (PET). There is a high incidence of PET in women with renal disease during pregnancy and importance of diagnosis and safe treatment of hypertension during pregnancy is discussed. The authors present the current theories of the pathogenesis of PET and highlight the importance of prophylactic treatment with aspirin to reduce the risk of PET. Pregnancy is increasingly common following renal transplantation and this group requires special consideration. They may have other concurrent medical conditions that need to be considered during pregnancy, or they may be at higher risk of other medical complications e.g. urinary tract infection with potential implications for maternal health and foetal wellbeing. It is important to facilitate preconception counselling for women with pre-existing renal disease to discuss optimal timing of pregnancy, make necessary adjustments to medications, and to discuss the likely outcomes for mother and baby. Managing renal disease during pregnancy requires the input of nephrologists, obstetricians, midwives, and often other healthcare professionals which is optimally delivered in a multi-disciplinary antenatal clinic with an expertise in this area.

Management of advanced chronic kidney disease (CKD)

The number of patients with advanced kidney disease requiring dialysis is increasing in all parts of the world. Managing patients as they transition onto dialysis and providing support and guidance as they make important treatment choices are essential components of a nephrologist’s job. Ensuring timely preparation for dialysis, allowing patients the opportunity to explore all options, including conservative care, and managing individual expectations of dialysis are increasingly important. All nephrologists will manage patients treated with dialysis and therefore it is imperative that they have a sound understanding of different dialysis modalities, how to assess the adequacy of dialysis, and the commonly encountered medical problems dialysis patients experience.

Fluid and electrolyte disorders

Fluid and electrolyte disorders are very common in nephrology practice. They may develop due to several disorders related directly with kidney disease, or with other conditions or drugs, etc., altering fluid and electrolyte physiology. Fluid and electrolyte disorders may usually present as an incidental finding in a blood test with mild or no symptoms, but may also present as a severe, life-threatening entity. Fluid and electrolyte disorders may present as single, isolated derangement of one electrolyte or as mixed problems. The prevention or prompt recognition and appropriate management of fluid and electrolyte disorders protect redundant morbidities and mortalities in many patients. This chapter covers disorders of sodium, potassium, calcium, phosphate and magnesium, and acid-base. It also discusses the clinical use of diuretics, which have dual effect on fluid-electrolyte disorders as aetiologic or therapeutic agents.

Diabetes and the kidney

Diabetic renal disease is the commonest cause of end-stage renal disease (ESRD) in the Western world and is rapidly becoming the leading cause in developing countries. The following chapters provide valuable insights into the epidemiology, pathophysiology, and pathology of diabetic renal disease with a focus on the clinical presentation, diagnosis, natural history, and progression of the disease. Many patients with diabetic renal disease suffer from microvascular and macrovascular complications of diabetes, including diabetic retinopathy, neuropathy, cardiovascular, and peripheral vascular disease. The authors discuss the available treatment approaches including lifestyle, diet, and exercise. In addition, they cover the importance of maintaining healthy blood pressure and glycaemic control to improve outcomes and the pharmacological treatments available. The authors describe the range of hypoglycaemic agents now available as well as insulin treatment. Ultimately, many patients will require management of complications of diabetes. Often they develop progressive renal impairment that requires renal replacement therapy with dialysis and transplantation, which are also discussed.

Tubular and interstitial disease

Tubulointerstitial diseases refer to a group of disorders in which inflammatory cell infiltrates within the kidney interstitium and/or tubular epithelium are seen on kidney biopsy. These disorders constitute an important group of kidney diseases with varying prevalences and presentations due to a number of causes. It is difficult to estimate the worldwide incidence of tubular and interstitial disease as it is a histological diagnosis and biopsy rates vary substantially around the world. Increasing incidence of tubulointerstitial nephritis has been related to polypharmacy, particularly in the older population. Tubulointerstitial nephritis may present acutely as an immunologically mediated hypersensitivity reaction to an inciting agent—typically a drug or infection—or chronically as a part of a disease process leading to chronic interstitial fibrosis and tubular atrophy. Allergic interstitial nephritis, analgesic nephropathy, nephrotoxic metals, hyperuricemia, Balkan nephropathy, Mesoamerican nephropathy, aristolochic acid nephropathy, and other rare causes of tubulointerstitial nephritis are covered in this section. Isolated defects of tubular function, tubular disorder-related nephropathies, and electrolyte derangements also constitute important aspects of tubulointerstitial diseases.

Glomerular disease

Glomerular diseases are common causes of end-stage kidney disease in many parts of the world. The epidemiology of glomerular diseases varies across countries, contributed in part by genetic predisposition and in part by differences in screening and biopsy practices. While glomerulonephritis could be considered a primary condition due to inherent pathologies in the kidneys, e.g. minimal change disease, focal segmental glomerulosclerosis, membranous nephropathy, and IgA nephropathy, it can be secondary to systemic conditions with distinct histopathological features on kidney biopsies. Likewise, even though histopathological patterns like mesangiocapillary and endocapillary glomerulonephritis may represent primary inflammatory features of kidney diseases, they may often manifest as a feature and be a suggestion of an underlying secondary systemic condition. For certain glomerular diseases, the natural history may be one of spontaneous remission, or may follow a remitting–relapsing course even with treatment. The approach to treatment involves general management measures to reduce proteinuria and provide symptomatic relief, with consideration for immunosuppression in those who present with significant morbidities or who have clinical features suggestive of a poor prognostic risk profile.

Hypertension

Hypertension (HTN) is a common condition and a risk factor for numerous comorbidities, including cardiovascular disease, cerebrovascular disease, and progressive renal disease. In many people the aetiology of HTN is unknown, but in some a triggering “secondary” cause can be identified, e.g. renal disease, endocrine, or other underlying condition. For most people the treatment of HTN is straightforward, but in a small number the blood pressure can become “malignant or accelerated” and require urgent treatment or hospitalization. The chapters in this section provide an overview of the clinical assessment and investigation of a hypertensive patient, the recommended lifestyle modifications and pharmacological treatment options available, and potential complications of HTN. Renal artery stenosis a common cause of HTN that can be caused by atheromatous renovascular disease (ARVD) or other rarer pathologies, including fibromuscular disease, Takayasu’s arteritis, or other syndromes. ARVD is the commonest cause of renal artery disease in the Western world and in this section the authors focus upon the epidemiology and clinical presentation of ARVD and the potential diagnostic and treatment strategies. A particular focus is given to the role of medical and interventional treatment of ARVD, including potential outcomes, complications, and prognosis.

General considerations in patients with renal disease

Kidney diseases represent a large spectrum of conditions with varying prevalences, presentations, outcomes, personal, and societal impact. Kidney disease is frequently diagnosed as an incidental finding in blood and urine tests. A carefully taken history and physical examination may point to clues for various kidney diseases. A complete examination of urine accompanied by assessment of proteinuria and albuminuria is one of the basic diagnostic evaluations. Assessment of glomerular filtration rate as the best index of kidney function is crucial for every patient with kidney disease. Several immunological tests on blood and urine may provide additional diagnostic information, assessment of prognosis, and response to treatment. Imaging of kidneys and urinary tract with various modalities may not only provide some diagnostic information, but also may give chances to treat some kidney diseases. A kidney biopsy may provide a specific diagnosis, reflect the level of disease severity, and guide to use appropriate treatment. Assessment of kidney functions are also essential for safe prescribing as the ability of the kidneys to handle drugs is significantly altered in kidney disease.

The child with kidney disease

As adult nephrologists we recognize the importance of understanding the evolution of kidney disease in children and young adults. We also acknowledge that in many parts of the world there is no distinction between adult and paediatric nephrology and therefore it is important that nephrologists have a sound grasp of paediatric and adult kidney diseases. Transition from paediatric to adult nephrology services is a challenging time for many young adults living with kidney disease and ensuring adult nephrologists appreciate the multiple and often unique challenges growing up with kidney disease bring is an important component of nephrology practice. It is also important that as adult nephrologists we understand the spectrum of kidney diseases that affect children and young adults, which are often markedly different to those we encounter in adult practice.