PAINE #PANCE Pearl – Renal

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Question

42yo woman, with a history systemic lupus erythematosus, presents to your clinic with a 1-month history of progressive leg swelling and polyuria. She is complaint with her medications and states that she hasn’t changed anything in her medical care. Physical examination reveals 2+ pitting edema to the knees in the lower extremities. BMP, UA, and urine microscopy are below.

  1. What is the next step in diagnosing this patient and what would you expect to find?

Answer

This patient found to heavy proteinuria on a urinalysis and oval fat bodies on urine microscopy, which would point to nephrotic syndrome as a diagnosis.

The next step in the diagnostic management of this patient would be to perform a 24-hour urine collection for urine protein. Normal urine protein excretion is < 150mg/day, but nephrotic range proteinuria is diagnostic at > 3.5g/day. Alternatively, a random urine protein-to-creatinine ratio of > 3.5 can be used, but is less reliable than a 24-hour collection.

Once a nephrotic syndrome diagnosis is made by urine studies, it should be followed up with a renal biopsy to determine the cause.

#51 – Renal Tubular Acidosis

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***LISTEN TO THE PODCAST HERE***

Definition

  • Group of disorders that cause a metabolic acidosis due to defects in the renal tubules
    • Net retention of HCl
    • Net loss of NaHCO3

Pathophysiology

The kidney regulates acid-base balance two main ways:

  • Reabsorption of filtered HCO3
    • >80% of the bicarbonate filtered by the glomerulus is reabsorbed in the proximal renal tubules via Na-H exchange
  • Acid excretion
    • Collecting ducts of the nephron excrete hydrogen ions buffered by NH3 and PO3 (so the pH of the urine doesn’t destroy the nephron)
      • Extra production of NH3 is stimulated by intracellular acidosis.
  • 3 step process
    • Reabsorption of sodium to create a negative gradient in the tubular lumen
    • Excretion of hydrogen by H-K-ATPase and reabsorption of potassium
    • Prevention of hydrogen ions from diffusing back out of the tubular lumen

Initial Presentation

  • Patients diagnosed with an RTA must first be diagnosed with a metabolic acidosis
    • Decreased pH with decreased HCO3
  • After this is determined, the anion gap must be calculated and found to be normal
    • AG = Na – (Cl + HCO3) = 8-12

Differential for NAGMA

  • Ureteric diversion
  • Small bowel fistulae
  • Excessive saline
  • Diarrhea
  • Carbonic anhydrase inhibitors
  • Renal tubular acidosis
  • Adrenal insufficiency
  • Pancreatic fistulae

Type I (distal) RTA

  • Cause
    • Defect in the distal hydrogen ion excretion
  • Pathophysiology
    • Failure of the H-ATPase proton pump (most common cause)
      • Inability to acidify urine < 5.5
      • Hypokalemia
    • Increased hydrogen ion permeability of the luminal membrane

Type II (proximal) RTA

  • Cause
    • Defect in proximal bicarbonate reabsorption
  • Pathophysiology
    • Damage to the proximal tubule that leads to progressive bicarbonate wasting in the urine

Type IV (hypoaldosteronism)

  • Cause
    • Reductions in aldosterone secretion and responsiveness
  • Pathophysiology
    • Decreased rate of proton secretion rather than an intrinsic defect in the tubule’s capacity to generate normal pH gradient
    • Hyperkalemia causes reduced urine NH4, which in turns leads to more acidic urine
      • Hydrogen ions have nothing to bind to

Diagnostic Work-Up

  • RTAs should be considered in any patient with a normal anion gap metabolic acidosis
    • Need ABG and BMP
  • Once this determination is made:
    • Urine pH
      • > 5.5 in type I (distal)
      • < 5.5 in type II (proximal) and type IV
    • Urine ammonium
      • Elevated in type II (proximal)
      • Decreased in type I (distal) and type IV
      • Most labs can’t measure urine ammonium directly:
        • Urine Anion Gap (urine Na+K+Cl)
          • (+) UAG = > 20
            • Type I (distal) and type IV
          • (-) UAG = < – 20
            • Type II (proximal)
    • Serum potassium
      • Elevated in type IV
      • Decreased in type I and II

Treatment

  • Type I (distal)
    • Urinarary Alkali Therapy
      • Sodium bicarbonate
        • Increased risk of nephrolithiasis due to bicarbonaturia
          • Use potassium citrate instead
  • Type II (proximal)
    • Much more difficult to treat due to the INCREASED bicarbonate diuresis during bicarbonate therapy
    • Alkali therapy (10x the dose for type I) AND potassium salt repletion as bicarbonaturia INCREASES urinary potassium losses
    • Thiazide diuretics if large alkali doses ineffective or not tolerated
      • Diuresis reduces urinary bicarbonate loss by increasing proximal sodium reabsorption
        • Which secondarily increased bicarbonate reabsorption
  • Type IV
    • Stop any medication causes or treat underlying condition (hypoaldosteronism)
      • Mineralcorticoid (fludrocortisone) and glucocorticoid (hydrocortisone)
    • Potassium repletion
Up-To-Date. 2019

References

  1. Rodríguez Soriano J. Renal tubular acidosis: the clinical entity. Journal of the American Society of Nephrology : JASN. 2002; 13(8):2160-70. [pubmed]
  2. Skelton LA, Boron WF, Zhou Y. Acid-base transport by the renal proximal tubule. Journal of nephrology. ; 23 Suppl 16:S4-18. [pubmed]
  3. Hamm LL, Nakhoul N, Hering-Smith KS. Acid-Base Homeostasis. Clinical journal of the American Society of Nephrology : CJASN. 2015; 10(12):2232-42. [pubmed]
  4. The Curbsiders.  Episode 104. https://thecurbsiders.com/internal-medicine-podcast/104-renal-tubular-acidosis-kidney-boy-joel-topf-md
  5. DB’s Medical Rants.  http://www.medrants.com/archives/8897
  6. Oh M, Carroll HJ. Value and determinants of urine anion gap. Nephron. 2002; 90(3):252-5. [pubmed]
  7. Rodríguez Soriano J. Renal tubular acidosis: the clinical entity. Journal of the American Society of Nephrology : JASN. 2002; 13(8):2160-70. [pubmed]
  8. Karet FE. Mechanisms in hyperkalemic renal tubular acidosis. Journal of the American Society of Nephrology : JASN. 2009; 20(2):251-4. [pubmed]

PAINE #PANCE Pearl – Renal

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Question

42yo woman, with a history systemic lupus erythematosus, presents to your clinic with a 1-month history of progressive leg swelling and polyuria. She is complaint with her medications and states that she hasn’t changed anything in her medical care. Physical examination reveals 2+ pitting edema to the knees in the lower extremities. BMP, UA, and urine microscopy are below.

  1. What is the next step in diagnosing this patient and what would you expect to find?

Ep-PAINE-nym

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Loop of Henle

Other Known Aliases – ansa nephroni

Definition – portion of the nephron that goes from the proximal convoluted tubule to the distal convoluted tubule. There are four portions of this structure:

  • Thin descending segment
  • Thin ascending segment
  • Ascending limb
  • Cortical thick ascending limp

Clinical Significance – the loop of Henle creates an area of high urea concentration with secretion and reabsorption of water and electrolytes. This is also the portion of the nephron where the aptly named “loop diuretics” to manage blood pressure by means of excess fluid excretion.

History – Named after Friedrich Gustav Jakob Henle (1809-1885), who was a German physician, pathologist, and anatomist and received his medical doctorate from the University of Bonn in 1832. He spent his early career as a prosector for Johannes Müller in Berlin where he published furiously on numerous facets of human and animal anatomy and physiology. He then went on to become the chair of anatomy at the University of Zurich, where he became one of the early adopters and advocates for the study of pathophysiology as a single distinct discipline. He also set the early argument for the germ theory in an essay entitled “On Miasma and Contagia”. His life’s work culminated in the publishing of the Handbook of Systematic Human Anatomy in 1855, which was the most complete and comprehensive work at that time.

References

  1. Firkin BG and Whitwirth JA.  Dictionary of Medical Eponyms. 2nd ed.  New York, NY; Parthenon Publishing Group. 1996.
  2. Bartolucci S, Forbis P.  Stedman’s Medical Eponyms.  2nd ed.  Baltimore, MD; LWW.  2005.
  3. Yee AJ, Pfiffner P. (2012).  Medical Eponyms (Version 1.4.2) [Mobile Application Software].  Retrieved http://itunes.apple.com.
  4. Whonamedit – dictionary of medical eponyms. http://www.whonamedit.com
  5. Up To Date. www.uptodate.com

Ep-PAINE-nym

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Jefferson Fracture

Other Known Aliases – none

Definition – burst fracture of C1 that results in a multi-part fracture of the anterior and posterior arches.

Clinical Significance – the most common mechanism of injury for Jefferson fractures is direct axial loading or hyperextension seen in diving injuries or falls. Most are unstable and require emergency stabilization via traction or halo placement while awaiting surgery.

History – Named after Sir Geoffrey Jefferson (1886-1961), who was a British neurologist and pioneering neurosurgeon, and received his medical doctorate from the University of Manchester in 1909. He had prolific career as a pioneering neurosurgeon in Manchester throughout the 1920s-30s culminating in performing the first surgical embolectomy in England in 1925 and becoming the first professor of neurosurgery at the University of Manchester in 1939. He published the description of his eponymous injuries in 1920 describing a series of four cases of similar injuries. Side note: He was also an advocate for advancements in surgical science and gave a ground-breaking lecture at the Royal College of Surgeons in 1949 entitled “The Mind of the Mechanical Man”, where he discussed one of the earliest electronic computers at Manchester and laid the foundation for the debate on artificial intelligence.

References

  1. Firkin BG and Whitwirth JA.  Dictionary of Medical Eponyms. 2nd ed.  New York, NY; Parthenon Publishing Group. 1996.
  2. Bartolucci S, Forbis P.  Stedman’s Medical Eponyms.  2nd ed.  Baltimore, MD; LWW.  2005.
  3. Yee AJ, Pfiffner P. (2012).  Medical Eponyms (Version 1.4.2) [Mobile Application Software].  Retrieved http://itunes.apple.com.
  4. Whonamedit – dictionary of medical eponyms. http://www.whonamedit.com
  5. Up To Date. www.uptodate.com
  6. Sir Geoffrey Jefferson 1886-1961. JNS. 1961;18(3):407-408. [article]
  7. Jefferson G. Fracture of the atlas vertebra. Report of four cases, and a review of those previously recorded. BJS. 1919;7(27):407-422. [article]

PAINE #PANCE Pearl – Orthopaedics

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Question

11yo male presents to pediatrician with a 3 week history of a painful left hip. He and his parents denies any inciting or traumatic event and he denies fever, chills, recent illness, or past symptoms. On physical examination, he has a noticeable limp and you elicit pain with passive internal rotation of the hip. Radiograph is below.

  1. What is the main risk factor for this condition?
  2. What radiographic abnormality is seen?
  3. What is the management of this condition?
  4. What is the most serious adverse event associated with this condition?

Answer

Diagnosis – Slipped Capital Femoral Epiphysis

1. The main risk factor is obesity in adolescence with > 60% of cases occurring in children ≥90th percentile weight for age.

2. Diagnosing SCFE on plain radiographs is accomplished by drawing a parallel line from the lateral femoral neck towards the femoral head. This line is called Klein’s Line. In normal patients, this line should intersect the lateral portion of the femoral head. In SCFE patient, it does not.

3. The mainstay of management of SCFE is operative stabilization by way of percutaneous in situ fixation

4. The most serious complication seen with SCFE is avascular necrosis of the femoral head, but other complications include chondrolysis and femoroacetabular impingement.

References

  1. Loder RT. The demographics of slipped capital femoral epiphysis. An international multicenter study. Clinical orthopaedics and related research. 1996; [pubmed]
  2. https://www.orthobullets.com/pediatrics/4040/slipped-capital-femoral-epiphysis-scfe
  3. http://www.wheelessonline.com/ortho/treatment_scfe

Ep-PAINE-nym

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Klein’s Lines

Other Known Aliases – Line of Klein

Definition – Virtual line drawn parallel from the femoral neck that should intersect the lateral upper edge of the femoral head

Clinical Significance – Used in the radiographical diagnosis of slipped capital femoral epiphysis and allows for early diagnosis and surgical management to prevent avascular necrosis as an adult. The sensitivity and specificity are the highest if modified by a ≥2mm difference in the epiphyseal width lateral to Klein’s line compared to the unaffected side.

History – Named after Armin Klein (1892-1954), who was an American orthopaedic surgeon and received his medical doctorate from Harvard Medical School in 1927. He completed his residency at Boston City Hospital and upon completion joined the faculty at Massachusetts General Hospital. It was here in 1952 that Klein and three colleagues published a case series on children with previously undiagnosed SCFE, but with positive findings using his technique. He would later go on to become Chief of Orthopaedic Surgery at the new Beth Israel Hospital in Boston and obtained teaching positions at Harvard Medical School and Tufts College Medical School.

References

  1. Firkin BG and Whitwirth JA.  Dictionary of Medical Eponyms. 2nd ed.  New York, NY; Parthenon Publishing Group. 1996.
  2. Bartolucci S, Forbis P.  Stedman’s Medical Eponyms.  2nd ed.  Baltimore, MD; LWW.  2005.
  3. Yee AJ, Pfiffner P. (2012).  Medical Eponyms (Version 1.4.2) [Mobile Application Software].  Retrieved http://itunes.apple.com.
  4. Whonamedit – dictionary of medical eponyms. http://www.whonamedit.com
  5. Up To Date. www.uptodate.com
  6. KLEIN A, JOPLIN RJ, REIDY JA, HANELIN J. Slipped capital femoral epiphysis; early diagnosis and treatment facilitated by normal roentgenograms. The Journal of bone and joint surgery. American volume. 1952; 34-A(1):233-9. [pubmed]
  7. https://journals.lww.com/jbjsjournal/Citation/1954/36040/ARMIN_KLEIN_1892_1954.29.aspx