Nephrology

During bedside rounds in the surgical intensive care unit, a critical care team evaluates a 68-year-old individual who underwent an emergency exploratory laparotomy 24 hours ago for acute mesenteric ischemia. The postoperative course has been complicated by massive fluid shifts and a need for continuous nasogastric tube suctioning, which is currently draining approximately 1,500 mL of bilious fluid daily. The patient is intubated and sedated. Vital signs demonstrate a blood pressure of 88/50 mm Hg and a heart rate of 122/min.

Serum laboratory analysis reveals:
$Na^+$: 142 mEq/L
$K^+$: 3.2 mEq/L
$Cl^-$: 88 mEq/L
$HCO_3^-$: 16 mEq/L
BUN: 45 mg/dL
Creatinine: 2.1 mg/dL

Arterial blood gas analysis on 40% $FiO_2$ demonstrates:
pH: 7.28
$P_{CO2}$: 34 mm Hg
$P_{O2}$: 92 mm Hg

Assuming a reference normal anion gap of 12 mEq/L and a reference normal bicarbonate of 24 mEq/L, calculate the patient's corrected bicarbonate level (often used to assess for a tertiary acid-base disorder via the delta-delta gap) in mEq/L.

A newly admitted 19-year-old male with a history of type 1 diabetes mellitus is evaluated on the medical ward for persistent nausea, recurrent vomiting, and diffuse abdominal pain. The patient admits to missing his insulin doses over the past three days. The following initial serum chemistry panel is obtained:

* Sodium: 138 mEq/L
* Potassium: 5.1 mEq/L
* Chloride: 99 mEq/L
* Bicarbonate: 14 mEq/L
* Blood urea nitrogen: 28 mg/dL
* Creatinine: 1.2 mg/dL
* Glucose: 485 mg/dL

Calculate the patient's serum anion gap in mEq/L.

Match each clinical and laboratory profile of hypokalemic metabolic alkalosis to its most likely underlying etiology.

A 28-year-old daycare worker comes to the urgent care center complaining of severe, watery diarrhea for the past four days. She reports drinking only tap water since her symptoms began and has been unable to keep solid food down. On physical examination, her blood pressure is 105/65 mmHg and her pulse is 112/min. Her mucous membranes are dry. Laboratory studies show:

Which of the following is the expected arterial partial pressure of carbon dioxide ($PaCO_2$) for this patient if appropriate respiratory compensation has occurred?

Match each classic urinalysis sediment finding with the renal pathology it most strongly indicates.

A 21-year-old male is brought to the emergency department by his roommate due to profound generalized weakness and episodes of confusion over the past 24 hours. The roommate mentions the patient was recently fired from his job at a paint manufacturing plant and has been spending most of his time locked in his room with a strong, unusual chemical odor. On physical examination, the patient is lethargic but arousable. Muscle strength is 2/5 in the bilateral lower extremities and 3/5 in the upper extremities. Deep tendon reflexes are diminished. His blood pressure is 110/70 mm Hg, heart rate is 98/min, and respiratory rate is 22/min.

Laboratory studies reveal the following:

Arterial blood gas on room air shows a pH of 7.28 and a $pCO_2$ of 26 mm Hg. Urinalysis reveals a pH of 6.8 with no protein or blood. Urine electrolyte testing reveals a sodium of 45 mEq/L, potassium of 25 mEq/L, and chloride of 30 mEq/L.

Which of the following is the most likely primary mechanism responsible for this patient's laboratory abnormalities?

A 42-year-old woman presents to the emergency department with a 2-day history of profound, generalized muscle weakness. She has a past medical history of rheumatoid arthritis and complains of chronic dry eyes and a dry mouth. She takes no daily medications. Her blood pressure is 118/76 mm Hg, heart rate is 88/min, and respiratory rate is 18/min. Physical examination reveals normal muscle bulk but symmetrically decreased proximal and distal muscle strength (3/5) in both the upper and lower extremities. Deep tendon reflexes are globally diminished. Laboratory evaluation reveals the following:

Serum chemistry:
Sodium: 139 mEq/L
Potassium: 2.1 mEq/L
Chloride: 114 mEq/L
Bicarbonate: 14 mEq/L
Blood urea nitrogen: 14 mg/dL
Creatinine: 0.9 mg/dL

Arterial blood gas (room air):
pH: 7.28
pCO2: 30 mm Hg
pO2: 95 mm Hg

Urinalysis:
pH: 6.8
Specific gravity: 1.015
Protein: Negative
Glucose: Negative
Ketones: Negative

Which of the following is the primary pathophysiologic mechanism underlying this patient's laboratory abnormalities?

A 45-year-old man comes to the emergency department reporting four days of frequent, large-volume watery stools. He feels weak and lightheaded when standing. Physical examination reveals dry mucous membranes, flat neck veins, and delayed capillary refill. Laboratory results are as follows:

Based on these findings, which of the following best describes this patient's primary acid-base disorder?

Match each set of laboratory findings with the most likely underlying etiology. Assume all patients are normotensive adults who are not currently taking any prescription medications.

A 62-year-old man is evaluated in the hospital for decreased urine output over the past 24 hours. He was admitted three days ago for the treatment of community-acquired pneumonia with intravenous antibiotics. His blood pressure is 110/70 mm Hg and his pulse is 88/min. Laboratory studies show:

Serum sodium: $140 \text{ mEq/L}$
Serum creatinine: $4.0 \text{ mg/dL}$
Urine sodium: $70 \text{ mEq/L}$
Urine creatinine: $80 \text{ mg/dL}$

Based on these laboratory values, what is this patient's fractional excretion of sodium (in percent)?

A 63-year-old man is brought to the emergency department by ambulance after vomiting a large amount of bright red blood. He has a history of alcohol use disorder and cirrhosis. On arrival, he is confused and lethargic. Temperature is 36.5°C (97.7°F), blood pressure is 85/50 mm Hg, and pulse is 124/min. Physical examination shows scleral icterus, spider angiomas on the chest, and a distended abdomen with a positive fluid wave. Two large-bore intravenous lines are placed, and fluid resuscitation is initiated.

Laboratory studies obtained prior to fluid administration show:

Serum:
Sodium: 140 mEq/L
Blood urea nitrogen: 68 mg/dL
Creatinine: 2.1 mg/dL

Urine:
Sodium: 12 mEq/L
Creatinine: 60 mg/dL

Calculate the patient's fractional excretion of sodium (in percent).

Match each clinical presentation and associated laboratory profile to the most likely underlying pathophysiologic mechanism.

A 19-year-old male is brought to the urgent care clinic by his parents due to extreme fatigue, increased thirst, and frequent urination over the past week. Today, he developed nausea and deep, rapid breathing. Laboratory evaluation shows:

Serum sodium: $138 \text{ mEq/L}$
Serum chloride: $104 \text{ mEq/L}$
Serum bicarbonate: $12 \text{ mEq/L}$

Arterial blood gas analysis on room air reveals:
pH: $7.24$
$PaCO_2$: $26 \text{ mm Hg}$
$PaO_2$: $95 \text{ mm Hg}$

Based on these findings, which of the following is the most accurate interpretation of this patient's acid-base status?

A 42-year-old male patient is admitted to the intensive care unit for the management of severe acute pancreatitis. On presentation, he was tachycardic and hypotensive. Over the initial 24 hours of admission, he received 7 liters of 0.9% sodium chloride intravenously for aggressive fluid resuscitation. His vital signs are now stable. Laboratory studies obtained on hospital day 2 reveal the following:

Serum sodium: $142 \text{ mEq/L}$
Serum potassium: $4.2 \text{ mEq/L}$
Serum chloride: $115 \text{ mEq/L}$
Serum bicarbonate: $15 \text{ mEq/L}$
Blood urea nitrogen: $18 \text{ mg/dL}$
Serum creatinine: $0.9 \text{ mg/dL}$

Arterial blood gas on room air shows:
pH: $7.28$
$PaCO_2$: $30 \text{ mmHg}$
$PaO_2$: $92 \text{ mmHg}$

Which of the following is the most likely mechanism underlying this patient's current acid-base abnormality?

A 22-year-old woman is brought to the emergency department 4 hours after intentionally ingesting an unknown quantity of pills. She complains of ringing in her ears, nausea, and diffuse abdominal pain. Her temperature is 37.8°C (100.0°F), blood pressure is 110/70 mm Hg, pulse is 115/min, and respirations are 26/min.

Which of the following best characterizes this patient's primary acid-base disturbance(s)?

Match each clinical presentation with its most likely primary acid-base disorder.

Match each clinical presentation and disease association to the most likely corresponding nephrotic syndrome etiology.

A 54-year-old man with a history of severe chronic obstructive pulmonary disease and major depressive disorder is brought to the emergency department by paramedics after being found unarousable in his garage. An open, empty container of antifreeze was found nearby. Vital signs are temperature 36.7°C (98.1°F), blood pressure 112/68 mmHg, pulse 110/min, and respirations 16/min. Pulse oximetry is 89% on room air. Physical examination reveals an obtunded patient with a barrel-shaped chest, diminished breath sounds, and diffuse bilateral wheezing.

Laboratory testing yields the following results:

Which of the following best describes this patient's current acid-base status?

A 65-year-old male with poorly controlled type 2 diabetes mellitus presents to the emergency department following 3 days of intractable vomiting, diffuse abdominal pain, and an inability to tolerate oral intake. He reports that he stopped taking his prescribed insulin regimen 48 hours ago due to his lack of appetite. On physical examination, he appears lethargic and mildly confused. His mucous membranes are completely dry, and he has markedly decreased skin turgor. His temperature is 37.1°C (98.8°F), blood pressure is 90/60 mm Hg, pulse is 112/min, and respiratory rate is 24/min.

Laboratory studies show the following:
Sodium: $142 \text{ mEq/L}$
Potassium: $3.8 \text{ mEq/L}$
Chloride: $94 \text{ mEq/L}$
Bicarbonate: $16 \text{ mEq/L}$
Blood urea nitrogen: $45 \text{ mg/dL}$
Serum creatinine: $2.2 \text{ mg/dL}$
Glucose: $550 \text{ mg/dL}$
Serum ketones: large

Assuming a normal serum anion gap of $12 \text{ mEq/L}$ and a normal serum bicarbonate of $24 \text{ mEq/L}$, what is the delta ratio ($\Delta\text{AG} / \Delta\text{HCO}_3^-$) for this patient?

A 24-year-old woman with a history of type 1 diabetes mellitus presents to the emergency department with nausea, vomiting, and diffuse abdominal pain. She reports missing her insulin doses for the past two days due to illness. On physical examination, she appears lethargic. Her blood pressure is 105/65 mm Hg, heart rate is 118/min, and respiratory rate is 26/min with deep, rapid breaths. Laboratory studies show the following:

What is the patient's calculated serum anion gap? (Provide the numerical value in mEq/L).