Paediatric Nephropathy PDF

PEDIATRIC NEPHROLOGY Anatomy & Physiology The kidneys lie in the retroperitoneal space slightly above the level of the umbilicus. They range in length and weight, respectively, from approximately 6 cm and 24 g in a full-term newborn to 12 cm or more and 150 g in an adult. T...

PEDIATRIC NEPHROLOGY Anatomy & Physiology The kidneys lie in the retroperitoneal space slightly above the level of the umbilicus. They range in length and weight, respectively, from approximately 6 cm and 24 g in a full-term newborn to 12 cm or more and 150 g in an adult. The kidney has an outer layer, the cortex, which contains the glomeruli, proximal and distal convoluted tubules, and collecting ducts, and an inner layer, the medulla, which contains the straight portions of the tubules, the loops of Henle, the vasa recta, and the terminal collecting ducts. Anatomy & Physiology Anatomy & Physiology Anatomy & Physiology The blood supply to each kidney usually consists of a main renal artery that arises from the aorta. The main artery divides into segmental branches within the medulla and these into interlobar arteries that pass to the junction of the cortex and medulla. The interlobar arteries branch to form the arcuate arteries. Interlobular arteries originate from the arcuate arteries and give rise to the afferent arterioles of the glomeruli. The afferent arteriole divides into the glomerular capillary network, which then merges into the efferent arteriole. Anatomy & Physiology As the blood passes through the glomerular capillaries, the plasma is filtered through the glomerular capillary walls. The ultrafiltrate, which is cell free, contains all the substances in the plasma (electrolytes, glucose, phosphate, urea, creatinine, peptides, low molecular weight proteins) except proteins (like albumin and the globulins) having a molecular weight of 68,000 or more. The filtrate is collected in Bowman space and enters the tubules, where its composition is modified by solute and fluid secretion and absorption until it leaves the kidney as urine. Anatomy & Physiology Anatomy & Physiology Although glomerular filtration begins around the 9th wk of fetal life, kidney function is not necessary for normal intrauterine homeostasis because the placenta serves as the major excretory organ. After birth, the glomerular filtration rate (GFR) increases until growth ceases toward the end of the 2nd decade of life. Anatomy & Physiology Anatomy & Physiology Tubular function Compared to adults there is reduced sodium and bicarbonate reabsorption and limited hydrogen ion excretion. The pH of urine is higher. Plasma osmolality Concentration capacity is limited. The maximal osmolality in infants is 700 – 800 mOsm/kg. Older children can achieve 1200 – 1400 mOsm/kg.  Glomerular Diseases Glomerular injury may be a result of genetic, immunologic, or coagulation disorders. There appear to be two major mechanisms of immunologic injury: (1) localization of circulating antigen-antibody immune complexes (2) interaction of antibody with local antigen in situ. The antigen may be a normal component of the glomerulus or an antigen deposited in the glomerulus.  Acute Poststreptococcal Glomerulonephritis Etiology  Acute poststreptococcal glomerulonephritis follows infection of the throat or skin by certain “nephritogenic” strains of group A β- hemolytic streptococci.  The factors that allow only certain strains of streptococci to be nephritogenic remain unclear. Acute Poststreptococcal Glomerulonephritis Pathogenesis  Although morphologic studies and a depression in the serum complement (C3) level strongly suggest that post- streptococcal glomerulonephritis is mediated by immune complexes, the precise mechanisms by which nephritogenic streptococci induce complex formation remain to be determined. Acute Poststreptococcal Glomerulonephritis  Acute Poststreptococcal Glomerulonephritis ClINICAL MANIFESTATIONS  Poststreptococcal glomerulonephritis is most common in children aged 5–12 yr and uncommon before the age of 3 yr. The typical patient develops an acute nephritic syndrome 1–2 wk after an antecedent streptococcal pharyngitis.  The severity of renal involvement varies from asymptomatic microscopic hematuria with normal renal function to acute renal failure.  Edema, hypertension, and oliguria may develop.  Acute Poststreptococcal Glomerulonephritis Clinical Manifestations  Patients may develop encephalopathy and/or heart failure owing to hypertension or hypervolemia.  Specific symptoms such as malaise, lethargy, abdominal or flank pain, and fever are common. The acute phase generally resolves within 6–8 wk.  Urinary protein excretion and hypertension usually normalize by 4–6 wk after onset.  Persistent microscopic hematuria may persist for 1–2 yr after the initial presentation. Acute Poststreptococcal Glomerulonephritis Diagnosis HISTORY - Latent period after pharyngeal infections CLINICAL PRESENTATION -GROSS HEMATURIA -EDEMA -OLIGURIA -HYPERTENSION LABORATORY FINDINGS: CBC, UREA, CREATININE, ELECTROLYTES, URINE, CULTURES, AST, C3, C5 Acute Poststreptococcal Glomerulonephritis Differential diagnosis  Glomerular hematuria Thin basement membrane disease (benign familial hematuria) Alport syndrome IgA nephropathy Hemolytic uremic syndrome Membranoproliferative glomerulonephritis Lupus nephritis Anaphylactoid purpura (Henoch-Schönlein purpura) Acute Poststreptococcal Glomerulonephritis Nonglomerular hematuria  Fever  Strenuous exercise  Mechanical trauma  Menstruation  Foreign bodies  Urinary tract infection  Hypercalciuria/urolithiasis  Sickle cell disease/trait  Coagulopathy  Tumors  Drugs/toxins (NSAIDs,anticoagulants)  Anatomic abnormalities (hydronephrosis, polycystic kidney disease, vascular malformations) Acute Poststreptococcal Glomerulonephritis Therapy Supportive and directed toward the potential complications Hospitalization is indicated if the child has significant hypertension or a combination of oliguria, generalized edema, and elevation of serum creatinine or potassium Bedrest, fluid restriction, antihypertensive drugs