19 Renal System

VVK19-001
Metabolic compensation of respiratory disorders.

Disorder	Metabolic Compensation
Acute respiratory acidosis	( ${HCO}_{3}^{-}$ ) increase by 1 for each 10 mm Hg increase in ( ${PCO}_{2}$ )
Chronic respiratory acidosis	( ${HCO}_{3}^{-}$ ) increase by 3.5 for each 10 mm Hg increase in ( ${PCO}_{2}$ )
Acute respiratory alkalosis	( ${HCO}_{3}^{-}$ ) decrease by 2 for each 10 mm Hg decrease in ( ${PCO}_{2}$ )
Chronic respiratory alkalosis	( ${HCO}_{3}^{-}$ ) decrease by 4 for each 10 mm Hg decrease in ( ${PCO}_{2}$ )

Answer

Disorder	Expected Compensation
Acute respiratory acidosis	( ${HCO}_{3}^{-}$ ) increases by 1 mEq/L for each 10 mm Hg increase in ${PCO}_{2}$
Chronic respiratory acidosis	( ${HCO}_{3}^{-}$ ) increases by 3.5–4 mEq/L for each 10 mm Hg increase in ${PCO}_{2}$
Acute respiratory alkalosis	( ${HCO}_{3}^{-}$ ) decreases by 2 mEq/L for each 10 mm Hg decrease in ${PCO}_{2}$
Chronic respiratory alkalosis	( ${HCO}_{3}^{-}$ ) decreases by 4–5 mEq/L for each 10 mm Hg decrease in ${PCO}_{2}$

VVK19-002
You receive KUB ultrasound report of a 4-year-old child. His height is 100 cm and weight is 22 kg. His serum creatinine is 1 mg/dL.

a. What is his approximate bladder capacity?
b. What is the volume considered to be significant for post void urine?
c. You suspect a renal tract abnormality, what is the investigation of choice to rule out scarring?
d. Calculate his GFR using Schwartz formula.

Answer

a. Bladder capacity $= (Age in years + 2) \times 30 = (4 + 2) \times 30 = 180 mL$
b. $> 20 mL$ (or $> 2 mL/kg$ ; $44 mL$ for this 22 kg child)
c. $^{99 m} Tc$ -DMSA (Dimercaptosuccinic acid) renal scan
d. $GFR = \frac{k \times Height (cm)}{Serum Creatinine (mg/dL)} = \frac{0.55 \times 100}{1} = 55 {mL/min/1.73 m}^{2}$

VVK19-003
Fractional excretion of sodium. Given below is the serum and urinary electrolyte report of a 6-year-old child:

Investigation	Value
$U_{{Na}^{+}}$	100 mEq/L
$U_{Cr}$	90 mg/dL
$U_{{Cl}^{-}}$	90 mEq/L
$U_{K^{+}}$	25 mEq/L
$S_{{Na}^{+}}$	135 mEq/L
$S_{Cr}$	1 mg/dL
$S_{{Cl}^{-}}$	100 mEq/L
$S_{K^{+}}$	4 mEq/L

a. Calculate ${Fe}_{Na}$ .
b. ${Fe}_{Na}$ is _________ than 1% with acute tubular necrosis.
c. ${Fe}_{Na}$ is _________ than 1% with severe obstruction of the urinary drainage of both kidneys.
d. ${Fe}_{Na}$ is _________ than 1% with acute glomerulonephritis.
e. ${Fe}_{Na}$ is _________ than 1% with hepatorenal syndrome.
f. ${Fe}_{Na}$ is _________ than 1% with states of prerenal azotemia such as congestive heart failure or dehydration.

Answer

a. ${Fe}_{Na} = \frac{U_{Na} \times S_{Cr}}{S_{Na} \times U_{Cr}} \times 100 = \frac{100 \times 1}{135 \times 90} \times 100 = 0.82 %$ (or $\approx 0.8 %$ )
b. Greater
c. Greater
d. Less
e. Less
f. Less

VVK19-004
Serum osmolality. Attached are serum reports of a 7-year-old child:

${S Na}^{+} : 140 mEq/L$
$S Cr : 1 mg/dL$
${S Cl}^{-} : 100 mEq/L$
${S K}^{+} : 4 mEq/L$
$S Glucose : 90 mg/dL$
$BUN : 14 mg/dL$

a. Calculate his serum osmolality.
b. What is the normal range?

Answer

a. $Calculated Osmolality = 2 \times {Na}^{+} + \frac{Glucose}{18} + \frac{BUN}{2.8} = 2 \times 140 + \frac{90}{18} + \frac{14}{2.8} = 280 + 5 + 5 = 290 mOsm/kg$ (or $285.5 mOsm/kg$ )
b. 275–290 mOsm/kg (or 275–295 mOsm/kg)

VVK19-005
Serum ${Na}^{+} = 136 mEq/L$ , ${Cl}^{-} = 102 mEq/L$ and ${HCO}_{3}^{-} = 10 mEq/L$ .

a. What is the anion gap?
b. What is the normal anion gap?
c. What is the likely anion gap in following (normal or increased)?

i. Diarrhea
ii. Lactic acidosis
iii. DKA
iv. ARF
v. RTA
vi. Salicylate poisoning
vii. Urinary tract diversion
viii. IEM
ix. Septic shock
x. Post hypocapnea

Answer

a. $Anion Gap = {Na}^{+} - ({Cl}^{-} + {HCO}_{3}^{-}) = 136 - (102 + 10) = 24 mEq/L$
b. 8–16 mEq/L (or 10–14 mEq/L)
c.
- i. Diarrhea — Normal
- ii. Lactic acidosis — Increased
- iii. DKA — Increased
- iv. ARF — Increased
- v. RTA — Normal
- vi. Salicylate poisoning — Increased
- vii. Urinary tract diversion — Normal
- viii. IEM — Increased
- ix. Septic shock — Increased
- x. Post hypocapnea — Normal

VVK19-006
A 9-month-old male infant is admitted in PICU with bacterial meningitis. His mean BP is 38 mm Hg. His laboratory reports are as follows:

Serum sodium: 126 mEq/L
Serum potassium: 4.2 mEq/L
Urine output: 4.7 mL/kg/h
Urinary sodium: 151 mEq/L

a. What is the cause of hyponatremia in this child?
b. List 2 investigations which will help in confirming the diagnosis.
c. How will you correct the electrolyte imbalance?
d. List two symptoms of hyponatremia.

Answer

a. Cerebral salt wasting (CSW)
b. Serum uric acid, serum vasopressin (ADH) level, central venous pressure / volume status assessment
c. 3% NaCl (Hypertonic saline) infusion. Treatment consists of restoring intravascular volume with sodium chloride and water, replacing ongoing urinary sodium losses (volume-for-volume), and treating the underlying acute brain injury.
d. Convulsions/seizures, irritability, altered sensorium/lethargy

VVK19-007
Given below are the reports of a 4-year-old male child admitted with a diagnosis of severe pneumonia. He is neurologically normal and has a urine output of 1.2 mL/kg/hr. His laboratory reports are as follows:

Serum sodium: 129 mEq/L
Serum potassium: 4.1 mEq/L
Urinary sodium: 31 mEq/L
Urinary potassium: 12 mEq/L

a. What is the most likely condition causing this electrolyte abnormality?
b. List 4 causes other than pneumonia which can lead into this condition.
c. How will you treat this condition?

Answer

a. SIADH (Syndrome of Inappropriate Antidiuretic Hormone Secretion)
b. Any 4 of:
- 1. Excessive administration of vasopressin in the treatment of central diabetes insipidus
- 1. Encephalitis
- 1. Brain tumors
- 1. Head trauma
- 1. Psychiatric disease
- 1. Postictal period after generalized seizures
- 1. Prolonged nausea
- 1. Tuberculous meningitis
- 1. AIDS
- 1. Hypothalamic-pituitary surgery
- 1. Drugs: Oxcarbazepine, carbamazepine, chlorpropamide, vinblastine, vincristine, and tricyclic antidepressants
c. Fluid restriction (restrict fluid intake to 50–75% of maintenance). SIADH is characterized by hyponatremia, inappropriately concentrated urine (>100 mOsm/kg), normal or slightly elevated plasma volume, normal-to-high urine sodium, and low serum uric acid.

VVK19-008
A 3-year-old male child presented in pediatric OPD with a history of 1 episode of abnormal movement 2 hours back. Parents also give history of oliguria and irritability for past 36 hours. He also has a 3-day history of bloody stools which stopped 3 days back. Parents were giving ORS for past 3 days. On examination, he is pale, edematous, has hepatomegaly, and has petechiae all over the body. His HR is 140/min, BP is 100/60 mm Hg. His arterial blood gas shows mild metabolic acidosis.

a. What is the most likely diagnosis?
b. What is the most likely etiology/pathogen involved in the above diagnosis?
c. List two differential diagnoses.
d. List 2 electrolyte abnormalities which can be associated with this diagnosis.

Answer

a. Hemolytic Uremic Syndrome (HUS)
b. E. coli O157:H7 (Enterohemorrhagic E. coli / Shiga toxin-producing E. coli) or Shigella dysenteriae type 1
c. Any 2:
- 1. Acute glomerulonephritis (PSGN)
- 1. Dyselectrolytemia
- 1. Intussusception
- 1. Thrombotic thrombocytopenic purpura (TTP) / DIC
d. Hyponatremia, hyperkalemia (or hypernatremia, hypocalcemia, hyperphosphatemia)

VVK19-009
Study the DTPA scan shown below and answer the questions.

VVK-P-Osce 19. Renal System_page_2_Picture_13.jpeg

a. What is the diagnosis on this DTPA scan?
b. What do DTPA and DMSA stand for?

Answer

a. Absent left-sided kidney perfusion / Non-functioning left kidney
b.
- DTPA: $^{99 m} Tc$ -labeled Diethylenetriaminepentaacetic acid scan
- DMSA: Dimercaptosuccinic acid scan

VVK19-010
A 12-year-old boy is brought to the clinic with recurrent cramps. On examination, his growth is normal. He is normotensive and has no evidence of rickets. His systemic examination is normal. His laboratory reports are as follows:

Hb: 12.1 g/dL
BUN: 8 mg/dL
Serum creatinine: 0.4 mg/dL
Serum sodium: 141 mEq/L
Serum potassium: 2.5 mEq/L
Serum chloride: 90 mEq/L
Serum magnesium: 0.5 mmol/L (low)
Urinary chloride: 35 mEq/L
Blood gas: pH 7.52, ${HCO}_{3}^{-}$ 30 mEq/L

a. What is the most probable diagnosis?
b. What is the mode of inheritance?
c. What is the treatment?

Answer

a. Gitelman's syndrome
b. Autosomal recessive
c. Potassium and magnesium supplements

VVK19-011
Match the following:

Histology / Glomerular Pathology	Disease
a. Diffuse mesangial proliferative	1. Alport syndrome
b. Focal segmental	2. IgA nephropathy
c. With crescents	3. RPGN
d. Foam cells	4. Poststreptococcal glomerulonephritis

Answer

a. Diffuse mesangial proliferative — 4. Poststreptococcal glomerulonephritis (or 2. IgA nephropathy)
b. Focal segmental — 2. IgA nephropathy (or FSGS)
c. With crescents — 3. RPGN (Rapidly progressive glomerulonephritis)
d. Foam cells — 1. Alport syndrome

VVK19-012
A 16-year-old female, known case of SLE presents to pediatric OPD with intermittent hemoptysis and hematuria. On examination, she is noted to be pale and hypertensive. On investigation, her complement levels were normal. Further investigation revealed antibodies to lung and glomerular basement membrane.

a. What is the most likely diagnosis?
b. What is the most likely cause of hemoptysis in this patient?
c. List 2 treatment options.

Answer

a. Goodpasture disease (Anti-GBM disease)
b. Pulmonary hemorrhage (diffuse alveolar hemorrhage)
c.
- Pulsed methylprednisolone
- Immunosuppression (e.g., Cyclophosphamide)
- Plasmapheresis (plasma exchange)

VVK19-013
A 3-year-old female child is reviewed in pediatric OPD for failing to thrive and abdominal pain. Her investigation revealed Hb 10 g/dL, serum sodium of 136 mEq/L, serum potassium of 2.9 mEq/L and metabolic acidosis. Her urinary pH was 6.1. On further evaluation, she is diagnosed to have renal stones.

a. What is the most likely diagnosis including the subtype of the pathology?
b. What is the underlying pathogenesis?
c. What is the treatment?

Answer

a. Type I (Distal) Renal Tubular Acidosis (RTA)
b. Impaired distal urinary acidification / defective $H^{+}$ ion secretion in the collecting duct
c. Bicarbonate supplementation, potassium replacement, thiazide diuretics

VVK19-014
A 2-year-old female child is reviewed in pediatric OPD for short stature. She also complains of polyuria and polydipsia. Her examination revealed signs of rickets. Her investigation showed serum sodium of 137 mEq/L, serum potassium of 2.8 mEq/L and metabolic acidosis. Her urinary pH was 4.9.

a. What is the most likely diagnosis including the subtype of the pathology?
b. What is the underlying pathogenesis?
c. What is the treatment?

Answer

a. Type II (Proximal) Renal Tubular Acidosis (RTA)
b. Impaired proximal tubular ${HCO}_{3}^{-}$ reabsorption
c. High-dose oral bicarbonate supplementation (and potassium supplementation, vitamin D / phosphate if rickets is present)

VVK19-015
Given below is the photograph of an 8-day-old male neonate. He is also diagnosed to have undescended testis and urinary tract abnormality.

VVK-P-Osce 19. Renal System_page_4_Picture_7.jpeg

a. What is the diagnosis?
b. What are the associated urinary tract abnormalities with this condition?
c. Give 1 pulmonary complication associated with this condition.

Answer

a. Prune-Belly syndrome (Eagle-Barrett syndrome / Triad syndrome)
b. Dilated ureters (megaureter), megalourethra, large hypoplastic bladder, hydronephrosis, vesicoureteral reflux (VUR)
c. Pulmonary hypoplasia / pneumothorax

VVK19-016
A 4-year-old child with nephrotic syndrome presents with fever, vomiting, severe abdominal pain and abdominal distension. On examination, his HR is 160/min along with shallow and rapid breathing. His blood tests reveal peripheral leucocytosis with a marked predominance of polymorphonuclear cells.

a. What is the diagnosis?
b. How would you confirm the diagnosis?
c. What is the most likely cause/pathogen/organism for the same?
d. What is the immediate treatment?

Answer

a. Spontaneous bacterial peritonitis (SBP)
b. Diagnostic ascitic tap: PMN count $> 250 cells/ μ L$ (with PMNs $> 50 %$ ) and ascitic fluid culture
c. Streptococcus pneumoniae (Pneumococci), followed by E. coli
d. Parenteral antibiotic therapy (e.g., IV cefotaxime / 3rd generation cephalosporin with or without an aminoglycoside)

VVK19-017
A $1 \frac{1}{2}$ -year-old child presents with failure to thrive, muscle weakness, constipation and polyuria. His arterial blood gas shows:

$pH : 7.52$
${PCO}_{2} : 45 mm Hg$
${HCO}_{3}^{-} : 35 mEq/L$

a. What is your interpretation of the ABG?
b. List 4 clinical conditions in which this ABG finding can be seen.
On further investigation, he was noted to have hypokalemia.
c. List 2 possible diagnoses.
His urine shows hypercalciuria.
d. What is the diagnosis?
e. How do you treat this patient?

Answer

a. Metabolic alkalosis (uncompensated / partially compensated)
b. Any 4 of:
- Gastric losses (emesis or nasogastric suction)
- Diuretic use
- Gitelman syndrome
- Bartter syndrome
- Exogenous base/alkali administration
- Autosomal dominant hypoparathyroidism
- Adrenal adenoma or hyperplasia / Primary hyperaldosteronism
- Glucocorticoid-remediable aldosteronism
- Renovascular disease
- Renin-secreting tumor
- Cushing syndrome
c. Gitelman syndrome, Bartter syndrome
d. Bartter syndrome (characterized by hypokalemic metabolic alkalosis and hypercalciuria)
e. Potassium supplementation, adequate hydration, sodium chloride supplementation, nutritional support, and indomethacin / NSAIDs / potassium-sparing diuretics (spironolactone / amiloride).

VVK19-018
A 3-year-old female presented to pediatric OPD with complaint of irritability and lethargy. On examination, she appears pale. On further questioning mother gave history of URTI 1 week back for which she consulted a local physician who conservatively treated it as viral URI. She also gave history of decreased urine output. After a week of the above illness, she became irritable and lethargic. Child's blood investigations revealed a BUN of 81 mg/dL and serum creatinine of 4.2 mg/dL. Her blood gas shows pH of 7.18 and serum K of 5.6 mmol/L with tall T waves in the ECG. Her platelet count is 85,000/mm³.

a. What is the diagnosis?
b. What are the possible findings on the peripheral smear of this child?
c. What is the most common organism associated with this disease?
d. List 2 indications of dialysis in this child.

Answer

a. Hemolytic Uremic Syndrome (HUS) — atypical presentation (more commonly presents following gastroenteritis, but occasionally can follow URI/pneumococcal infection).
b. Microangiopathic hemolytic anemia with schistocytes (fragmented RBCs, burr cells, helmet cells), thrombocytopenia, and leukocytosis.
c. E. coli O157:H7 (~70–80% of D+ HUS) / Streptococcus pneumoniae (for D- / atypical post-URI HUS).
d. Indications for dialysis in this child:
- Severe refractory hyperkalemia ( $K^{+} > 5.5 – 6.0 mEq/L$ with ECG changes)
- Severe metabolic acidosis ( $pH < 7.20$ ) refractory to medical management
- Uremic encephalopathy / seizures / fluid overload / severe oliguria-anuria

VVK19-019
Given below is the picture of a 6-year-old boy presenting in OPD with complaint of severe abdominal pain of 1 day duration. On examination, he is noted to have similar rash over buttocks and thighs. His CBC and clotting profile is normal.

VVK-P-Osce 19. Renal System_page_5_Picture_13.jpeg

a. What is the most likely diagnosis?
b. What is the prognosis?
c. What are the factors associated with worst prognosis?
d. List 2 possible long-term complications.

Answer

a. Henoch-Schönlein purpura (IgA vasculitis)
b. Generally favorable (97–98% resolve completely)
c. Factors associated with worse renal prognosis:
- Acute nephritic and/or nephrotic syndrome at presentation
- Severe renal involvement (crescents on $> 50 %$ of glomeruli on renal biopsy)
- Persistent heavy proteinuria
- Older age at onset
d. Any 2:
- Chronic renal failure / chronic kidney disease
- Persistent hypertension
- Microscopic or gross hematuria / persistent proteinuria
- Pregnancy-induced hypertension later in life

VVK19-020
What is the dietary requirement for a child with acute renal failure in terms of:

a. Calorie requirement.
b. Protein requirement.
c. Sodium requirement.
d. Potassium intake.
e. Phosphorus.

Answer

a. Calories: Maximized — at least the daily requirement of 100 kcal/kg/day (or age-appropriate requirement).
b. Protein: Restrict moderately (0.6–1.0 g/kg/day of high biological value protein to minimize azotemia).
c. Sodium: Restrict, no added salt (1–2 mEq/kg/day).
d. Potassium: Restrict, avoid potassium-containing food (<1 mEq/kg/day or eliminate during oliguria).
e. Phosphorus: Restrict (avoid dairy and high-phosphate foods, use phosphate binders).