Tablet Mecobalamin - Dosage

Standard Tablet Dosage

Injection Dosage (for comparison)

• Peripheral neuropathy: 500 mcg IM/IV, 3 times per week
• Megaloblastic anemia: 500 mcg IM/IV, 3 times per week for 2 months, then reduce to once every 1-3 months for maintenance

Evidence supports IM 500 mcg three times weekly over a single high dose of 1,500 mcg weekly - it produces significantly higher serum cobalamin levels (Korean J Pain, 2018).

Indications for Tablet Form

• Peripheral neuropathy (diabetic, alcoholic, drug-induced, entrapment)
• Lumbago and intercostal neuralgia
• Diabetic retinopathy
• B12 deficiency states
• Bell's palsy, multiple sclerosis (adjunct)

Key Points

• Take after meals to reduce GI upset
• Not recommended in children (data insufficient)
• Treatment duration: minimum 4-6 weeks to assess benefit; full nerve regeneration may take months
• No upper toxicity limit established for mecobalamin (water-soluble vitamin)
• Store away from light (photosensitive)

Calot's Triangle (Hepatocystic Triangle)

Definition

Borders

The modern definition replaced the cystic artery (a structure inside the triangle) with the liver edge as the superior border - this allows better landmark identification before the cystic artery is even dissected.

Contents

• Cystic artery (usually a branch of the right hepatic artery, >90% of cases)
• Right hepatic artery (may loop into the triangle)
• Lymph node of Lund (node of Calot) - used as a landmark
• Connective tissue and lymphatics
• Occasionally: accessory hepatic ducts or accessory arteries

Surgical Importance

1. Clearing the triangle of Calot of all fat and fibrous tissue
2. Freeing the base of the gallbladder from the liver
3. Only two structures seen entering the gallbladder - the cystic duct and cystic artery

• Failure to achieve CVS is the most common cause of bile duct injuries
• Anatomy is "normal" in only ~30% of individuals - anomalies are the rule
• The most dangerous variant: cystic duct joining a low-lying aberrant right sectoral duct

• Perform subtotal cholecystectomy, or
• Convert to open surgery

Anatomical Variants to Know

• Cystic duct may insert into the right hepatic duct (not the common hepatic duct)
• Cystic artery may arise from the left hepatic, proper hepatic, or gastroduodenal artery
• Double cystic artery: an anterior and posterior branch may arise separately
• Aberrant right hepatic duct passing through the triangle

History

AST/ALT Ratio in Alcoholic Liver Disease (De Ritis Ratio)

The De Ritis Ratio - Quick Summary

Key Values

In alcoholic hepatitis, the AST:ALT ratio is typically >3:1, with a mean ratio of ~2.6 (vs. 0.9 in non-alcoholic fatty liver disease). - Quick Compendium of Clinical Pathology, p. 34-48

Why Is AST Disproportionately Elevated in Alcoholism?

1. Vitamin B6 (pyridoxal-5'-phosphate) deficiency - common in alcohol-dependent patients due to malnutrition. ALT is more dependent on vitamin B6 as a cofactor than AST. B6 depletion preferentially reduces ALT synthesis/activity, pushing the ratio toward AST dominance.
2. Direct mitochondrial injury by alcohol - ~80% of AST is concentrated in mitochondria. Alcohol causes direct mitochondrial damage, releasing large amounts of mitochondrial AST into circulation. ALT is exclusively cytoplasmic, so it is not amplified by this mechanism.

• Yamada's Textbook of Gastroenterology, p. 805

Statistical Performance

• Symptom to Diagnosis, p. 9976-9999

Important Caveats

• Not exclusive to alcohol: AST:ALT > 2 can also occur in:
  • Wilson's disease
  • Hepatic cirrhosis (any cause, due to progressive fibrosis)
  • Liver neoplasia
  • Hepatitis C-related cirrhosis
• Absolute levels are usually modest: In ALD, transaminases rarely exceed 300-400 U/L (even in severe alcoholic hepatitis). Very high transaminases (>1000 U/L) suggest another diagnosis (ischemic hepatitis, viral hepatitis, drug toxicity).
• High ratio may indicate advanced disease, not just heavy drinking: A high AST:ALT may reflect advanced alcoholic liver disease (cirrhosis) rather than simply indicating an active binge.
• GGT synergy: Combining AST:ALT >2 with an elevated GGT significantly increases specificity for alcoholic etiology.

Comparison Across Liver Diseases

Tender Hepatomegaly - Differential Diagnosis

Causes of TENDER Hepatomegaly

1. Infective / Inflammatory

"An enlarged tender liver could signify viral or alcoholic hepatitis; an infiltrative process such as amyloidosis; or, less often, an acutely congested liver secondary to right-sided heart failure." - Harrison's Principles of Internal Medicine 22E

2. Vascular / Congestive

"Hepatomegaly is an early sign of systemic venous congestion. The liver edge may be tender due to stretching of the capsule, but with progression of right HF, tenderness may disappear." - Harrison's 22E, p. 2027

3. Infiltrative (may be tender or non-tender)

Causes of NON-TENDER Hepatomegaly

Key Clinical Rule