Nephrology Lecture #5

_____________ is a sudden decrease in renal function (over hours to days) which affects fluid balance, electrolyte balance and nitrogen excretion

Acute kidney injury

What would acute kidney injury do to creatinine and BUN?

Increase

A 64-year-old male with a history of poorly controlled diabetes and chronic hypertension presents to the emergency department with progressive confusion, fatigue, and abdominal discomfort over the past few days. His family notes that he has not urinated in over 24 hours. On examination, his blood pressure is 178/100 mmHg, and he is disoriented to time and place. He is noted to have a flapping tremor when asked to extend his arms and dorsiflex his wrists. Cardiovascular exam reveals distant heart sounds and a friction rub. Abdominal exam shows diffuse tenderness without rebound. Laboratory tests show elevated BUN and creatinine, hyperkalemia, and metabolic acidosis.

What is the diagnosis?

What is the criteria for acute kidney injury?

1.) Absolute increase in serum creatinine by 0.3mg/dL or more within 48 hours

2.) Relative increase > 1.5 known baseline within 7 days

3.) Decrease in urine volume to less then 0.5 mL/kg over 6 hours

What is the urine output criteria for AKI?

Urine output of less then 0.5mL/kg/hour for more then 6 hours

What is the classic presentation of prerenal AKI?

Decreased renal perfusion pressure

What is the classic presentation of intrinsic AKI?

Pathology of vessels, glomeruli, or tubulointerstitium

What is the classic presentation of postrenal AKI?

Obstructive

What would you see on an EKG of AKI?

Hyperkalemia - peaked T waves, PR prolongation, QRS widening

Hypocalcemia - Long QT interval

____________describes the flow rate of filtered fluid through the glomerulus

Glomerular filtration

______________ is the volume of blood plasma that is cleared of creatinine per unit time and is a useful measure for approximating the GFR

Creatinine clearance

How do you diagnose AKI?

Radiographic imaging, serologic testing,

What is the most common type of AKI?

Prerenal

What is the BUN levels for prerenal AKI?

BUN: Cr> 20:1

Which type of AKI is related to volume depletion, low cardiac output, and change in vascular resistance?

Pre-renal

BUN: Cr >20:1

Pre-Renal AKI

What is the least common cause of AKI?

Post-renal AKI

Which type of AKI is related to obstruction of urine from both kidneys?

Post-renal AKI

Why is FeNA less then 1 in pre-renal AKI?

Kidney is conserving sodium because of decreased renal perfusion

A 76-year-old man is brought to the emergency department after several days of vomiting and diarrhea. He appears lethargic and hypotensive. On exam, his mucous membranes are dry, and skin turgor is poor. His blood pressure is 88/56 mmHg, and heart rate is 112 bpm. Lab results show:

BUN: 68 mg/dL

Creatinine: 2.4 mg/dL

Urine sodium: 8 mEq/L

Urine creatinine: High

Urinalysis: Benign, with no blood or protein, and hyaline casts

Urine osmolality: 620 mOsm/kg

What is most likely the cause of this patient's AKI?

Prerenal azotemia

A 79-year-old man presents with acute-onset lower abdominal discomfort and decreased urine output over the past two days. He reports a history of benign prostatic hyperplasia (BPH) and recently started taking diphenhydramine for sleep. On exam, he is mildly hypertensive and has a firm, distended lower abdomen. Bedside bladder scan reveals >600 mL of retained urine. Labs show elevated BUN and creatinine. Urinalysis is benign, with no protein or blood. Renal ultrasound reveals bilateral hydronephrosis.

What is the most appropriate initial step in management?

A) Initiate IV fluids for prerenal azotemia

B) Begin corticosteroids for interstitial nephritis

C) Insert a Foley catheter

D) Start loop diuretics and monitor output

What is the diagnosis?

What imaging can you order?

How do you treat it?

C) Insert a Foley catheter

1.) Post-renal AKI

2.) Bladder scan to a assess residual urine

Renal ultrasound

Cross sectional Imaging CT or MRi

3.) Relieve obstruction

______________________is the most common intrinsic kidney injury, occurs due to damage of the tubular cells of the kidney from ischemic or nephrotoxic causes

Acute tubular necrosis

What is the main difference between prerenal AKI and intrinsic AKI?

Prerenal is obstruction before kidney, intrinsic is damage to the kidney from necrosis or lack of perfusion.

A 63-year-old man is admitted to the hospital for septic shock secondary to pneumonia. He received aggressive fluid resuscitation and broad-spectrum antibiotics. On day 3 of hospitalization, his urine output decreases significantly, and labs show a rising creatinine level. He is hemodynamically stable on low-dose vasopressors. Urinalysis reveals muddy brown granular casts. FeNa is calculated at 3.5%.

What is the most likely cause of this patient's acute kidney injury?

A) Prerenal azotemia due to hypovolemia

B) Post-renal obstruction due to urinary retention

C) Acute tubular necrosis from ischemic injury

D) Acute interstitial nephritis due to antibiotics

How do you treat it?

C) Acute tubular necrosis from ischemic injury

Intrinsic acute Kidney Injury

1.) Prevent further kidney injury, remove toxins, treat sepsis, improve renal perfusion, loop diuretics

FeNa> 2

acute tubular necrosisi

Interstitial Nephritis triad

Rash

Fever

Eosinophils

What is this condition called, its an inflammatory process of renal tubules. Often caused by medications. It typically presents with rash, fever, and eosinophils.

Interstitial Nephritis

A 42-year-old woman presents with a 3-day history of fever, rash, and malaise. She was recently treated for a urinary tract infection with trimethoprim-sulfamethoxazole (TMP-SMX). She now reports decreased urine output and diffuse arthralgias. On physical exam, she has a maculopapular rash over her trunk and extremities. Labs reveal elevated serum creatinine and BUN. Urinalysis shows pyuria, hematuria, and white blood cell casts with eosinophils. Peripheral blood smear confirms eosinophilia.

What is the diagnosis?

How do you treat it?

1.) Interstitial nephritis

2.) Remove offending medication, limit salt and protein

Solve the riddle.

I am an inflammatory process of glomerulus with immune complex deposition. I present with edema, tea colored urine, red cell casts, proteinuria, and hematuria. You often need a renal biopsy to diagnose me. What am I?

Glomerularnephritis

A 10-year-old boy is brought to the clinic by his mother due to swelling around his eyes and decreased urine output for the past two days. She mentions he had a sore throat about two weeks ago that resolved without antibiotics. On exam, the boy has periorbital edema and elevated blood pressure. Urinalysis reveals tea-colored urine, proteinuria, hematuria, and red blood cell casts. His serum creatinine is elevated. An ASO titer is positive.

What is the most likely diagnosis?

A) IgA nephropathy

B) Acute interstitial nephritis

C) Post-streptococcal glomerulonephritis

D) Minimal change disease

How do you treat?

C) Post-streptococcal glomerulonephritis

1.) Low salt, protein diet, observation

_______________ is a state of acute muscle necrosis that can lead to several forms of systemic insult.

Rhabdomyolysis

What is rhabdomyolysis?

Its a state of acute muscle necrosis that can lead to several forms of systemic insult.

What is rhabdomyolysis?

Rhabdomyolysis is a serious medical condition caused by the breakdown of skeletal muscle tissue, leading to the release of muscle cell contents — especially myoglobin, creatine kinase (CK), potassium, and phosphate — into the bloodstream.

Why do you treat rhabdomyolysis when showing signs of acute kidney injury with aggressive hydration and IV fluids?

It aims to dilute circulating myoglobin and support renal prefusion

A 25-year-old man is brought to the emergency department after being found unconscious in a park following a suspected overdose. He had been lying immobile on the cold ground for several hours. On exam, he is confused, hypotensive, and has diffuse muscle tenderness. Labs reveal:

Creatine kinase (CK): 18,000 U/L (normal <200)

Potassium: 6.2 mEq/L

Creatinine: 2.1 mg/dL (baseline unknown)

Urinalysis: Dark brown urine positive for blood but no red blood cells on microscopy

What is most likely the patient's condition?

What is the classic triad for this condition?

How do you treat it?

What is the best laboratory test to order to diagnose rhabdomyolysis?

1.) Rhabdomyolysis

2.) muscle pain, weakness, dark colored urine

3.) Fluids and address the underlying cause

- Hyperkalemia should be treated

- Hypocalcemia should not be treated unless severe cardiac arrhythmias

- Hyperphosphatemia should not be corrected initially because it promotes increased calcium deposition in muscles

4.) Creatinine Kinase - Most specific marker

- Greater then 5000 units/L

What are some acute indications for dialysis?

Acidosis - metabolic acidosis and pH under 7.1

Electrolytes - Hyperkalemia

I-Intoxications

SLIME - Salicylates, Lithium, isopropanol, methanol, ethylene glycol

O - Overload

U - Uremia

- Elevated BUN with signs or symptoms of uremia

Which condition is associated with abnormal kidney function and progressive decline in GFR?

CKD

The stage of CKD where the accumulation of toxins, fluid, and electrolytes leads to death

UNLESS patient undergoes renal replacement therapy

ESRD

______________informally refers to any decline in kidney function that evolves over more than 48 hours but less than three months

subacute kidney injury

What are the two ways kidneys get damaged in CKD?

1.) Initial damage from underlying cause

2.) Hyperfiltration and hypertrophy of remaining nephrons

A 58-year-old man with a 15-year history of poorly controlled type 2 diabetes and hypertension presents for routine evaluation. He reports mild fatigue but denies swelling, shortness of breath, or urinary symptoms. Physical exam is unremarkable. Lab results show:

Creatinine: 2.1 mg/dL

eGFR: 42 mL/min/1.73m²

Urinalysis: Proteinuria (+2)

Microalbumin/Creatinine ratio: Elevated

BP: 152/88 mmHg

What best explains the progression of his kidney disease?

A) Immune complex deposition causing glomerular inflammation

B) Obstruction of urinary outflow causing back pressure

C) Hyperfiltration injury and glomerular hypertrophy of remaining nephrons

D) Direct toxic injury to tubular cells

C) Hyperfiltration injury and glomerular hypertrophy of remaining nephrons

When GFR is less then _________ for 3 months or more, CKD is present.

60

Which stages of CKD are asymptomatic?

Stage 1 and 2

Which stage of CKD is marked by disturbance of water and electrolyte homeostasis and eventually leads to uremic syndrome.

Stage 5

What is the most frequent cause of CKD in North American and Europe?

Diabetic nephropathy

What would the pH be and bicarb levels be with CKD?

pH is low and there is metabolic acidosis so bicarb is also low.

A 66-year-old woman with a history of long-standing hypertension, type 2 diabetes, and hyperlipidemia presents to the clinic for follow-up. She reports increasing fatigue and occasional leg swelling. She takes lisinopril, atorvastatin, and metformin. Labs from today reveal:

Creatinine: 2.8 mg/dL (up from 1.9 six months ago)

eGFR: 25 mL/min/1.73m²

Hb: 9.4 g/dL

Calcium: 8.1 mg/dL

Phosphorus: 5.6 mg/dL

PTH: 180 pg/mL

Urinalysis: +2 protein, no hematuria

Which of the following best explains her current laboratory findings?

A) Acute tubular necrosis

B) Chronic kidney disease with secondary hyperparathyroidism

C) Post-streptococcal glomerulonephritis

D) Minimal change disease

How do you treat it?

B) Chronic kidney disease with secondary hyperparathyroidism

1.) treat reversible causes of CKD

A 61-year-old man with stage 5 chronic kidney disease (CKD) secondary to long-standing diabetes and hypertension presents to the clinic with worsening fatigue, pruritus, anorexia, and difficulty concentrating. He has been following a renal diet and taking his medications as prescribed. Despite this, his recent labs show:

eGFR: 7 mL/min/1.73 m²

BUN: 95 mg/dL

Creatinine: 8.4 mg/dL

Potassium: 6.1 mEq/L

Bicarbonate: 17 mEq/L

Physical exam reveals bilateral lower extremity edema and poor skin turgor. He reports unintentional weight loss of 10 pounds in the past 2 months.

What is the most appropriate next step in management?

A) Begin erythropoietin therapy

B) Refer for urgent renal biopsy

C) Start oral sodium bicarbonate

D) Initiate renal replacement therapy

D) Initiate renal replacement therapy

Renal artery stenosis is a major cause of ________________.

renovascular hypertension

A 72-year-old man with a history of type 2 diabetes and hyperlipidemia presents with worsening blood pressure control despite adherence to a regimen of three antihypertensive medications. He also reports recent episodes of shortness of breath and orthopnea. At his last visit, an ACE inhibitor was added, but he developed an acute rise in serum creatinine from 1.4 to 2.6 mg/dL within a week. On physical examination, a bruit is heard over the right upper quadrant/flank.

What is the most likely underlying cause of this patient's condition?

A) Acute tubular necrosis

B) Bilateral renal artery stenosis

C) Uncontrolled essential hypertension

D) Chronic glomerulonephritis

What is the gold standard diagnostic imaging test?

Would you have hypokalemia or hyperkalemia?

B) Bilateral renal artery stenosis

1.) Renal angiography

2.) Hypokalemia

Beads on a string appearance on renal angiography

Renal artery stenosis

Red Blood Cell casts

Acute glomerulonephritis

White Blood cell casts

Acute interstitial nephritis

Waxy casts

Chronic ATN/Glomerulonephritis

Fatty casts: Oval bodies

Nephrotic syndrome

A 72-year-old man with a history of type 2 diabetes and hyperlipidemia presents with worsening blood pressure control despite adherence to a regimen of three antihypertensive medications. He also reports recent episodes of shortness of breath and orthopnea. At his last visit, an ACE inhibitor was added, but he developed an acute rise in serum creatinine from 1.4 to 2.6 mg/dL within a week. On physical examination, a bruit is heard over the right upper quadrant/flank.

What is most likely the underlying cause of this patient's condition?

What is the most likely underlying cause of this patient's condition?

A) Acute tubular necrosis

B) Bilateral renal artery stenosis

C) Uncontrolled essential hypertension

D) Chronic glomerulonephritis

How do you treat this?

B) Bilateral renal artery stenosis

1.) Control hypertension, angioplasty, surgical bypass surgery

What is it called when there is acute ischemic damage to the kidney, usually from thromboembolism or in situ thrombus?

Acute renal infaraction

A 55-year-old man with a history of atrial fibrillation not on anticoagulation presents to the emergency department with sudden-onset left flank pain, nausea, and vomiting that began 24 hours ago. He denies urinary symptoms. Vital signs reveal a blood pressure of 162/92 mmHg and a temperature of 99.9°F. Physical exam is notable for left flank tenderness but no costovertebral angle tenderness. Urinalysis is unremarkable. Serum creatinine is elevated compared to baseline. Contrast enhanced CT shows wedge-shaped perfusion defect

What is the most likely diagnosis?

A) Pyelonephritis

B) Nephrolithiasis

C) Renal artery infarction

D) Acute interstitial nephritis

How do you treat it?

C) Renal artery infarction

1.) Consult vascular surgery, evaluate thromboembolic risk, manage hypertension

Contrast CT - Wedge shaped Perfusion defect

Acute renal infaraction

Does rhabdomyolysis cause high or low FaNa?

High