Renal Flashcards
Calculate Anion gap
NA+K - HC03+Cl
ddx for NAGMA metabolic acidosis
- Renal tubular acidosis (RTA) 2. Excessive HCO3 loss from GIT
What is reabsorbed in the proximal tubule?
Glucose, amino acids, protein, vitamins, lactate, urea, uric acid, Na, K, Ca, Mg, , HC03, H20
not Cl
What disorders cause Fanconi’s syndrome?
hint) there are three causes and only 2 are disorders
Inherited tubular disorders : cystinosis, Dents, Lowes
Metabolic disorders: wilsons, tyrosinaemia, hereditary fructose intolerance, galactosemia, type 1 glycogen storage disease,
drugs: aminoglycosides, valproate, cisplatin, ifosfamide
heavy metal toxicity
What is Fanconi’s syndrome?
Generalised impairment of procimal tubule function.
Bicarbonate loss (Type 2 RTA)
Glycosuria
Hypophosphatemia
aminoaciduria
LMW proteinuria
What are the types of RTA?
Type 1: distal RTA (impaired secretion of H+ in distal nephron)
Type 2: proximal RTA
Type 4: Hyperaldosteronism
describe what happens in distal RTA
Distal (type 1) renal tubular acidosis (RTA) is characterized by impaired hydrogen ion secretion in the distal nephron, which reduces the kidney’s ability to excrete the daily acid load (50 to 100 mEq on a typical Western diet). This results in progressive hydrogen ion retention and a normal anion gap (or hyperchloremic) metabolic acidosis. If untreated, the plasma bicarbonate concentration can fall below 10 mEq/L.
Inability to excrete daily acid load
Progressive loss of buffer
Serum HCO3- < 10mmol/L
UpH >5.6
Hypokalaemia and sodium wasting
Hypercalciuria with risk of stones and nephrocalcinosis
Positive urinary anion gap (Na + K - Cl)
Describe what happens in proximal RTA
RTA is caused by defects that reduce the capacity to reclaim filtered bicarbonate in the proximal tubule, there are 3 processes by which bicarbonate is reclaimed by the body. Abnormalities of one or more of the multiple proximal tubule transporters, pumps, or enzymes can impair sodium bicarbonate reabsorption and cause the bicarbonate wasting found in proximal RTA
Distal reabsorption modifies HCO3- loss Serum HCO3- usually 12-20mmol/L Bicarb wasting only occurs when plasma HCO3- is > renal threshold.
HCO3- infusion causes alkaline urine (pH>7.5)
Describe what happens in type 4 Renal Tubular acidosis
reduced aldosterone effect (aldosterone maintains proper water balance by enhancing Na+ reabsorption and K+ secretion from extracellular fluid of the cells in kidney tubules.)
plasma bicarb >17mmol/L, urine pH <5.3, hyperkalemia, normal urinary calcium
describe the 3 clin presentations of Bartter’s Syndrome
what diuretic (chronic ingestion) does this mimic?
Hypokalaemia, hypochloraemia, metabolic alkalosis
normotensive, hyperreninaemia
Increased urinary excretion of K, Cl and Na
UrinaryCl>10mmol/L
Hypercalciuria
Polyuria, polydipsia, vomiting, constipation, salt craving,
tendency to dehydration, FTT Fatigue, weakness and cramps Developmental delay Nephrocalcinosis
various genetic defects that cause Bartter syndrome directly or indirectly reduce the activity of one of several electrolyte transporters in the thick ascending limb.
Loop diuretic
describe the pathophysiology of Bartter’s syndrome
Hereditary tubulopathy (group of) Can be considered as impaired Na+ and Cl- reabsorption in thick ascending limb (TAL) of Loop of Henle (LoH)
◦ Similar to action of frusemide
Increased K+ secretion distally
Decreased Ca++ reabsorption in LoH (coupled to Na-K-2Cl)
Bartter’s: Differential Diagnosis?
Diuretic use (no increase in urinary PGE2 and no improvement with indomethacin). Laxative abuse, vomiting or bulimia (extra renal states of chloride depletion)-exclude by measuring urinary chloride. Mineralocorticoid excess (hypertension). Mitochondrial cytopathies with proximal tubular dysfunction (Kearns Sayre and Fanconi Syndrome can both mimic Bartter in infancy).
Gitelman’s Syndrome; describe the major features and genetics
Hypokalaemia & hypomagnesaemia
Transient episodes of weakness and tetany
May have alkalosis
Urinary calcium low
Autosomal recessive ◦ NCCT gene (SLC12A3)
Diminished NaCl transport in distal CT
Like chronic thiazide use
Treat with magnesium
describe the features of Diabetes insipidus
Diagnosis
◦ Polyuria in a dehydrated child + hypernatraemia
◦ Normal maximal urinary osmolality 800-1200 mmol/l decreased to 350-600 mmol/l.
◦ Lack of response to DDAVP distinguishes from central DI
treatment of DI
Treatment
◦ Water
◦ Thiazides + amiloride (or indomethacin)
◦ Growth failure & developmental delay are both less likely with early treatment
Where is sodium maximally reabsorbed in the kidney
- Proximal tubule 60% (reg. by angiotensin)
- Thick Ascending limb of LoH 30% (reg. by aldosterone)
- Distal Convoluted tubule 5-8% (reg. by aldosterone)
- Collecting Duct 2% (reg. by aldosterone)
Define nephritis
Acute nephritic syndrome, characterized by red to brown urine, proteinuria (which can reach the nephrotic range), edema, hypertension, and an elevation in serum creatinine, which demonstrates inflammation In contrast to the protein losing Nephrosis. Often only C3 will be decreased as the
Ddx for Nephritis and major defining fx?
- C3 glomerulopathy (hematuria, hypertension, proteinuria, and hypocomplementemia, which may follow an upper respiratory infection in some patients. However, patients with C3 glomerulopathy continue to have persistent urinary abnormalities and hypocomplementemia beyond four to six week)
- IgA nephropathy − Patients with IgA nephropathy often present after an upper respiratory infection, similar to the presentation of patients with PSGN. Potential distinguishing features from PSGN include a shorter time between the antecedent illness and hematuria (less than 5 versus more than 10 days in PSGN) and a history of prior episodes of gross hematuria since recurrence is rare in PSGN.
- Secondary causes of glomerulonephritis − Lupus nephritis and IgA vasculitis (IgAV; Henoch-Schönlein purpura [HSP]) nephritis share similar features to PSGN. However, extrarenal manifestations of the underlying systemic diseases and laboratory testing should differentiate them from PSGN.
Which pathway of the complement cascade is activated in PSGN, Atypical hemolytic uremic syndrome, C3 glomerulopathy
these glomerular diseases share uncontrolled activation of the alternative pathway as the defining pathophysiology
what is the difference between osmolarity and osmololality
osmolarity is the molar concentration of solute particles per litre of solution, whereas osmolality is the molar concentration of solute particles per kg of solvent (water) (1 mole of solute for how much water?)
Normal body fluids osmolality: 285mOsmol/kg H20, urine osmolality may vary between 60 and 1400mOsmol/kg H20
What cells respond to vasopressin and where are they in the nephron?
Principle (p) cells in the distal tubule respond to ADH
intercalated I cells that contain lots of mitochondria and secrete hydrogen ions
Renin: where is it produced and what does it do?
Produced by the kidney, renin acts on angiotensin I, which is converted to angiotensin II, which is a potent vasoconstrictor affecitng blood pressure, tubular absorption of Na+, and aldosterone secretion from the adrenal glands. Renin release is stimulated by sympathetic filtration of the granular cells or a decrease in filtrate (Na+) concentration. The latter can occur following a fall in plasma volume, vasodilation of the afferent arterioles and renal ischaemia.
Describe the pathway of Vitamin D
- steroid hormone produced in food and synthesised in the skin in the presence of sunlight.
- hydroxylated in the proximal tubules
- regulated by PTH, phosphate and negative feedback. Active Vit D is essential for the mineralisation of bone, and promotes absorption of calcium ions and phosphate from the gut.
What can pass through the glomerulus?
anything under the molecular weight of 70kDa (glucose, amino acids, Na, K, urea), and must be positively charged - due to the anions on the glomerular surface. protein bound molecules evven if positively charged cannot pass through.