Liver trauma

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Liver Trauma

The liver is the second most commonly injured abdominal organ in blunt trauma (after the spleen) and the most commonly injured organ in penetrating abdominal trauma. Its large size and fixed position make it vulnerable to both compression/shearing forces and direct laceration.

Epidemiology & Mechanisms

Type	Mechanism	Associated injuries	Mortality
Blunt	Compression, shearing, deceleration	Spleen, mesentery, kidney	Overall 10-30%; severe/high-velocity up to 60%
Penetrating (stab/gunshot)	Direct laceration	Chest, pericardium	Lower than blunt (injury usually more localised)

At-risk presentations:

Stabbing or gunshot to lower chest / upper abdomen
Crush injury with multiple rib fractures
High-speed road traffic accident
Bailey and Love's Short Practice of Surgery, 28th Ed.

AAST Liver Injury Grading Scale (2018 Revision)

The American Association for the Surgery of Trauma (AAST) Organ Injury Scale is the standard grading system, based on CT imaging, operative, and pathologic criteria:

Grade	AIS	Description
I	2	Subcapsular haematoma <10% surface area; laceration <1 cm depth; capsular tear
II	2	Subcapsular haematoma 10-50% SA; intraparenchymal haematoma <10 cm diameter; laceration 1-3 cm depth, <10 cm length
III	3	Subcapsular haematoma >50% SA; ruptured subcapsular/parenchymal haematoma; intraparenchymal haematoma >10 cm; laceration >3 cm depth
IV	4	Active bleeding contained within liver parenchyma (vascular injury); parenchymal disruption involving 25-75% of hepatic lobe or 1-3 Couinaud segments
V	5	Parenchymal disruption >75% hepatic lobe; juxtahepatic venous injuries (retrohepatic IVC / central major hepatic veins) with active bleeding extending into peritoneum

Key rules:

Advance one grade for multiple injuries (up to Grade III)
"Vascular injury" = pseudoaneurysm or arteriovenous fistula (focal contrast collection decreasing on delayed images)
"Active bleeding" = contrast collection that increases in size/attenuation on delayed phase CT
Current guidelines recommend dual arterial/portal venous phase imaging

CT image of a Grade IV liver laceration (right hepatic lobe) with active contrast extravasation (arrow):

Grade IV liver laceration on CT - Sabiston Textbook of Surgery

Sabiston Textbook of Surgery, 21st Ed., Table 36.10

Initial Resuscitation (ATLS Principles)

Airway - ensure patency; intubate and ventilate if gas exchange inadequate
Breathing - intercostal chest drains if pneumothorax/haemothorax suspected
Circulation - two large-bore cannulae; blood crossmatch (10 units); ABG
Labs - FBC, U&E, LFTs, clotting screen, glucose, amylase
Volume replacement - prioritise blood; activate major haemorrhage protocol early
Coagulopathy correction - FFP and cryoprecipitate empirically (standard coagulation profiles are inadequate to evaluate acute factor loss); thromboelastography (TEG) if available - these patients rapidly develop irreversible coagulopathy from fibrinogen/clotting factor depletion

Bailey and Love's Short Practice of Surgery, 28th Ed.

Management Algorithm

The key determinant of management is haemodynamic stability, not injury grade.

Figure 69.11 Algorithm for management of liver trauma - Bailey & Love

Haemodynamically Unstable

Immediate laparotomy - do not delay for CT
Further resuscitation on the operating table

Haemodynamically Stable

CT chest and abdomen with IV contrast (dual arterial/portal phase)
Majority are managed non-operatively (NOM)
Interventional radiology with hepatic artery embolisation for arterial bleeding - safe and effective
If conservative management succeeds: discharge after 8-10 days, avoid abdominal trauma, rescan at 6-8 weeks
Readmit promptly if fever, bleeding, or pain develops

Modern principle: Non-operative management is the default for haemodynamically stable patients, regardless of injury grade. Sabiston (2024) notes that NOM should be the approach of choice for haemodynamically stable patients even with high-grade injuries, given improvements in CT technology and endovascular/endoscopic support.

Bailey and Love's Short Practice of Surgery, 28th Ed.; Sabiston Textbook of Surgery, 21st Ed.

Surgical Approaches

When laparotomy is indicated:

Incision: "Rooftop" incision with midline extension to the xiphisternum and retraction of costal margins - gives excellent access to liver and spleen. A midline incision can be extended transversely to the right if needed.

Operative techniques (in order of escalation):

Manual compression / perihepatic packing - initial aim; compress parenchyma without caval compression (Figure 69.9 in Bailey & Love)
- Pack against natural contour of the diaphragm
- Avoid overzealous packing (risk of pressure necrosis and abdominal compartment syndrome)
- If packing controls bleeding: close abdomen, transfer to ICU, relook laparotomy in 24-72 hours
Pringle manoeuvre - occlusion of the hepatoduodenal ligament (portal triad) if packing fails
Resectional debridement - remove necrotic tissue; leave poorly perfused but viable liver
Hepatotomy with direct suture ligation - for accessible bleeding points
Anatomical resection / hepatic artery ligation - at tertiary hepatobiliary centres
Venovenous bypass - for grade V/VI injuries involving hepatic veins or IVC; requires full liver mobilisation, Pringle manoeuvre, and IVC occlusion above renal veins

Damage control surgery principle: If control is achieved with packing and facilities are inadequate, close the abdomen and transfer to a tertiary centre.

Bailey and Love's Short Practice of Surgery, 28th Ed.

Complications

Early

Complication	Management
Recurrent haemorrhage	Re-operation, embolisation
Sepsis / liver abscess	Antibiotics + US-guided aspiration once liquefied
Bile collection / biloma	US-guided aspiration ± drain
Biliary fistula	ERCP or percutaneous cholangiography ± stent for biliary decompression; resection if persistent
Haemobilia	Embolisation
Hepatic insufficiency	Supportive care (usually recovers if blood supply + biliary drainage to adequate remnant preserved)
Abdominal compartment syndrome	Decompressive laparotomy

Late

Complication	Notes
Biliary strictures	May appear years later; segmental/lobar stricture + atrophy managed expectantly; dominant extrahepatic stricture with obstructive jaundice treated endoscopically or with Roux-en-Y hepaticojejunostomy
Hepatic artery aneurysm	Embolisation
Arteriovenous fistulae	Hepatic a. to hepatic v. (causes cardiac failure); arterioportal (causes portal hypertension) - treated by embolisation
Arteriobiliary fistula (haemobilia)	Embolisation
Intra-abdominal collections	Drainage

Bailey and Love's Short Practice of Surgery, 28th Ed.

Summary Box (Key Points)

Liver trauma is 2nd most common abdominal injury after splenic trauma in blunt mechanisms, most common in penetrating trauma
Blunt injuries carry higher mortality (up to 60% in severe cases)
Management is driven by haemodynamic stability, not CT grade
Non-operative management succeeds in the majority of patients
ATLS principles; early major haemorrhage protocol; TEG-guided coagulopathy correction
Perihepatic packing + damage control laparotomy is the cornerstone of operative management
Specialist teams (liver surgeon, anaesthetist, interventional radiologist, endoscopist) improve outcomes

Sources:

Bailey and Love's Short Practice of Surgery, 28th Ed., Chapter 69 - Liver trauma
Sabiston Textbook of Surgery, 21st Ed., Chapter 36 - Hepatic Injuries (AAST Liver Injury Scale 2018 Revision)

Thyroid carcinoma

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Thyroid Carcinoma

Thyroid carcinoma is the most common endocrine malignancy. The vast majority arise from thyroid follicular epithelium; a minority arise from parafollicular C cells. Overall prognosis for differentiated types is excellent, but aggressive variants carry high mortality.

Classification & Frequency

Type	Cell of Origin	Frequency
Papillary thyroid carcinoma (PTC)	Follicular epithelium	~80% of all thyroid cancers
Follicular thyroid carcinoma (FTC)	Follicular epithelium	~5-15%
High-grade / poorly differentiated	Follicular epithelium	~5%
Anaplastic (undifferentiated)	Follicular epithelium	~1%
Medullary thyroid carcinoma (MTC)	Parafollicular C cells	<5%

Most high-grade, poorly differentiated, and anaplastic carcinomas arise by progression from well-differentiated PTC or FTC through acquisition of additional mutations - they and MTC are the major causes of mortality from thyroid cancer.

NIFTP (Noninvasive Follicular Thyroid Neoplasm with Papillary-like nuclear features) is a reclassified entity - formerly encapsulated noninvasive follicular variant PTC. It has essentially no malignant potential and does not require aggressive treatment, though surgery is needed for definitive diagnosis.

Robbins, Cotran & Kumar Pathologic Basis of Disease

Molecular Pathogenesis

Thyroid cancers predominantly involve the MAP-kinase (RAS-BRAF-MEK-ERK) and PI3K/AKT signaling pathways:

Fig. 24.18 Genetic alterations in follicle cell-derived malignancies of the thyroid - Robbins Pathologic Basis of Disease

Subtype	Key Mutations
Conventional PTC	BRAF V600E (up to 80%); RET/PTC translocations; NTRK1/3 fusions
Follicular neoplasms (FTC, NIFTP)	RAS gain-of-function (~50%); PAX8-PPARG translocation (t(2;3)(q13;p25)); PIK3CA; PTEN loss
Anaplastic / PDTC	TP53 loss-of-function; TERT promoter mutations (on top of above)
Medullary (MTC)	Germline RET mutations (familial/MEN-2); somatic RET mutations (~50% sporadic)

Environmental risk factor: Ionizing radiation exposure, especially in the first two decades of life (e.g., post-Chernobyl surge in childhood PTC with high-frequency chromosome rearrangements).

Robbins, Cotran & Kumar Pathologic Basis of Disease

1. Papillary Thyroid Carcinoma (PTC)

Epidemiology: Most common thyroid malignancy; female predominance; associated with prior radiation exposure.

Morphology

Solitary or multifocal lesions; well-circumscribed or infiltrative
Gross: Papillary foci visible on cut surface
Microscopic hallmarks:
- Branching papillae with fibrovascular stalks covered by cuboidal cells
- "Orphan Annie eye" / ground-glass nuclei - optically clear/empty appearance due to finely dispersed chromatin
- Intranuclear pseudo-inclusions and intranuclear grooves (cytoplasmic invaginations)
- Psammoma bodies - concentrically calcified structures in papillary cores (virtually absent in FTC and MTC)
- Lymphatic invasion common; vascular invasion uncommon in smaller lesions
- Cervical lymph node metastases in up to 50% of cases

Fig. 18.12 Papillary thyroid carcinoma histology - Robbins Basic Pathology

(A) Gross papillary structures; (B) well-formed papillae; (C) ground-glass "Orphan Annie eye" nuclei; (D) FNA showing intranuclear inclusions [arrows]

Clinical Features

Presents as painless neck mass (within thyroid or cervical lymph node metastasis)
FNA diagnosis based on characteristic nuclear features
10-year survival >95% - extremely indolent
Isolated cervical node metastases do NOT significantly affect prognosis (unlike most cancers)
Hematogenous metastases (most commonly lung) present at diagnosis in a minority
Prognosis worsened by: age >40 years, extrathyroidal extension, distant metastases

Papillary microcarcinoma (<10 mm): common, not associated with adverse outcomes. Active surveillance without surgery is an accepted approach in many centers (Japan data: ≥2/3 never progress).

Variants

Over 12 variants described. Most common: encapsulated follicular variant (PAX8-PPARG fusion common; nuclear features of PTC with follicular architecture).

Robbins Basic Pathology; Bailey and Love's Short Practice of Surgery, 28th Ed.

2. Follicular Thyroid Carcinoma (FTC)

Epidemiology: Female:male ratio 3:1; peak age 40-60 years. More common in iodine-deficient areas (decreased in iodine-sufficient regions).

Morphology

Single nodule; well-circumscribed or widely infiltrative
Microscopically: uniform cells forming small follicles resembling normal thyroid
Diagnosis requires capsular and/or vascular invasion - cannot be distinguished from follicular adenoma on FNA alone
Hürthle cell tumour: rare variant with oxyphil (Askanazy) cells; associated with poor prognosis

Clinical Features

Presents as a solitary cold nodule; rarely hyperfunctional
Metastasizes haematogenously - lung, bone, liver (unlike PTC which goes to lymph nodes)
Regional lymph node metastases uncommon
Mortality: <10% with minimally invasive FTC within 10 years; up to 50% with widely invasive FTC
Skull metastases are a classic radiological finding
Treatment: surgical excision; well-differentiated metastases may be RAI-avid and treated with radioiodine
Robbins Basic Pathology; Bailey and Love's Short Practice of Surgery, 28th Ed.

3. Anaplastic Thyroid Carcinoma

Epidemiology: Mean age 65 years; older patients. ~25% have a history of well-differentiated thyroid carcinoma; another ~25% have a concurrent well-differentiated tumor in resected specimen.

Morphology

Bulky masses growing rapidly beyond the thyroid capsule into adjacent neck structures
Highly anaplastic cells: large and pleomorphic, or spindle-shaped, or mixed
Foci of papillary/follicular differentiation may be present (suggesting origin from differentiated cancer)

Clinical Features

Grows rapidly despite therapy
Distant metastases common
Death in <1 year in most cases from aggressive local growth and compromise of vital neck structures
Mortality approaching 100%
Robbins Basic Pathology

4. Medullary Thyroid Carcinoma (MTC)

Origin: Parafollicular C cells (not follicular epithelium) - secretes calcitonin (key diagnostic marker and surveillance tool).

Epidemiology:

Sporadic (70%): peak incidence 5th-6th decade
Familial (30%): associated with MEN-2A, MEN-2B, or familial MTC without MEN syndrome - all caused by germline RET mutations
MEN-2A/2B-associated cases occur in younger patients including children

Morphology

Solitary nodule or multiple bilateral lesions (familial cases tend to be bilateral and multicentric)
Polygonal to spindle-shaped cells in nests, trabeculae, or gland-like structures
Amyloid deposits in stroma (derived from altered calcitonin molecules) - distinctive feature
Familial cases: multicentric C-cell hyperplasia in surrounding thyroid (precursor lesion)
May also secrete: somatostatin, serotonin, vasoactive intestinal peptide (VIP)

Clinical Features

Neck mass with compression effects (dysphagia, hoarseness)
VIP secretion can cause diarrhoea
Screening of relatives via calcitonin levels or RET mutation testing
Prophylactic thyroidectomy offered to MEN-2 kindred members carrying RET mutations
Elevated calcitonin used for diagnosis and postoperative surveillance
Robbins Basic Pathology

Staging (AJCC/TNM - Differentiated Thyroid Cancer)

A key feature of the AJCC system for differentiated thyroid cancer is age-based staging:

Stage	<55 years	≥55 years
I	Any T, any N, M0	T1-2, N0, M0
II	Any T, any N, M1	T2, N0, M0 or any N (nodal disease upstages)
III	-	T3 disease
IV	-	All T4 (locally invasive) or M1

All patients <55 years are Stage I unless they have distant metastases (Stage II).

Bailey and Love's Short Practice of Surgery, 28th Ed.

ATA Risk Stratification (2015 Guidelines)

Used to guide RAI therapy decisions:

Risk	Features	Recurrence Rate
Low	No local invasion; all macroscopic tumor resected; no aggressive histology; no vascular invasion; clinical N0 or ≤5 micro-nodal metastases; papillary microcarcinoma	1-2%
Intermediate	Microscopic perithyroidal invasion; RAI-avid neck metastases; aggressive histology (tall cell, columnar); PTC with vascular invasion; >5 pathologic N1 (all <3 cm)	Variable
High	Gross extrathyroidal extension; incomplete resection; distant metastases; pathologic N1 with any node ≥3 cm; FTC with extensive vascular invasion (>4 foci)	>50%

Schwartz's Principles of Surgery, 11th Ed.

Management

Surgery

Total thyroidectomy is standard for most differentiated thyroid cancers
Goal: remove macroscopic disease, reduce recurrence risk, minimize morbidity, and facilitate RAI if needed
Hemithyroidectomy may be appropriate for low-risk, small (<4 cm), unifocal tumors
Central neck dissection for clinically involved nodes or high-risk features
In MEN-2 carriers: prophylactic total thyroidectomy (timing guided by RET mutation codon)
RLN (recurrent laryngeal nerve) identification and preservation is mandatory

Radioiodine (RAI / ¹³¹I) Therapy

High-risk DTC: RAI recommended after total thyroidectomy (gross ETE, distant metastases)
Low-risk DTC: RAI NOT routinely recommended for papillary microcarcinoma
Intermediate-risk: RAI generally favored for microscopic ETE, large lymph nodes, extranodal extension
RAI detects and treats metastases in ~75% of patients; highly effective for lung micrometastases (>70% success) but poor for pulmonary macrometastases (<10%)
Normal thyroid tissue competes for iodine - total thyroidectomy maximises RAI efficacy

TSH Suppression

Postoperative levothyroxine to suppress TSH - reduces stimulation of residual DTC cells
Degree of suppression targeted to risk category

Surveillance

Thyroglobulin (Tg) is the primary tumour marker for DTC surveillance
- Note: TgAb (anti-thyroglobulin antibodies) interfere with Tg measurement
Neck ultrasound
RAI whole-body scan

Targeted Therapy / Systemic Options

Sorafenib, lenvatinib: VEGFR/multikinase inhibitors for RAI-refractory DTC
Vandetanib, cabozantinib: for progressive/metastatic MTC (RET inhibitors)
BRAF V600E inhibitors (dabrafenib + trametinib): approved for anaplastic thyroid carcinoma
Anaplastic thyroid carcinoma: combined modality - surgery if resectable, external beam radiotherapy, systemic therapy; prognosis remains very poor
Schwartz's Principles of Surgery, 11th Ed.; Goodman & Gilman's Pharmacological Basis of Therapeutics; Bailey and Love's Short Practice of Surgery, 28th Ed.

Prognosis Summary

Type	Prognosis
PTC	10-year survival >95%; excellent even with nodal metastases in young patients
FTC (minimally invasive)	<10% mortality at 10 years
FTC (widely invasive)	Up to 50% mortality at 10 years
MTC	Intermediate; depends on stage and RET mutation codon
Anaplastic	Near 100% mortality; median survival <6 months

Sources:

Robbins, Cotran & Kumar Pathologic Basis of Disease - molecular pathogenesis, morphology
Robbins & Kumar Basic Pathology - histology and clinical features
Bailey and Love's Short Practice of Surgery, 28th Ed., Chapter 55 - clinical management
Schwartz's Principles of Surgery, 11th Ed., Chapter 38 - ATA risk stratification, RAI
Goodman & Gilman's Pharmacological Basis of Therapeutics - targeted chemotherapy
Sabiston Textbook of Surgery, 21st Ed., Chapter 73 - surgical anatomy and thyroidectomy

Hypercalcemic investigation approch

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Hypercalcemia: Investigation Approach

Definition: Serum adjusted calcium >2.65 mmol/L (>10.6 mg/dL) on two occasions, OR ionized calcium >1.31 mmol/L (>5.25 mg/dL).

Step 1 - Confirm Hypercalcemia

Always measure both total calcium + serum albumin to calculate adjusted (corrected) calcium, OR measure ionized calcium directly.

Correction formula:

Adjusted Ca = Measured total Ca + 0.8 × (4.0 - measured albumin [g/dL])

Confirm on two separate occasions before proceeding.

Step 2 - Clinical Assessment (History & Examination)

Before any laboratory testing, a careful history and examination often points toward the cause:

Clinical clue	Likely cause
Asymptomatic, detected incidentally, months-years duration	Primary hyperparathyroidism (PHPT)
Acutely unwell, Ca >12 mg/dL, neurological symptoms, known malignancy	Malignancy-associated
Nephrolithiasis, months of symptoms	PHPT (chronic)
Family history of hypercalcaemia, MEN, FHH	Familial causes, MEN syndrome
Medications: lithium, thiazides, vitamin D supplements, antacids	Drug-induced
Known respiratory/skin disease, lymphadenopathy	Sarcoidosis / granulomatous disease
Bone pain + anaemia + renal impairment	Multiple myeloma
Prolonged bed rest / immobilization	Immobilization hypercalcemia
Thyroid symptoms (heat intolerance, tachycardia, tremor)	Thyrotoxicosis
Adrenal symptoms (fatigue, postural hypotension, hyponatraemia)	Adrenal insufficiency

Key point: >90% of hypercalcaemia cases are due to either primary hyperparathyroidism (commonest in outpatients) or malignancy (commonest in inpatients). All other causes account for <10%.

Harrison's Principles of Internal Medicine, 22nd Ed.; Goldman-Cecil Medicine

Step 3 - Initial Laboratory Panel

Test	Purpose
Serum calcium (total + albumin, or ionized)	Confirm and quantify hypercalcaemia
Serum phosphate	Low/normal in PHPT; elevated in malignancy with bone metastases and renal failure
Serum creatinine / eGFR	Assess renal function; renal failure alters management
Intact PTH (immunometric / double-antibody assay)	The single most important test - pivotal branch point
Serum alkaline phosphatase	Elevated in ~10% PHPT (high-turnover bone disease); elevated in bone metastases
FBC	Anaemia points to myeloma or malignancy
Serum protein electrophoresis (SPEP) / serum free light chains	Rule out multiple myeloma
Serum magnesium	Hypomagnesaemia can affect PTH secretion

Step 4 - The PTH Pivot Point (The Central Branch)

Intact PTH (using immunoradiometric or immunochemiluminescent double-antibody assays) is the cornerstone of the investigation - it is cost-effective to measure in ALL hypercalcaemic patients unless the cause is clinically obvious.

Investigation Algorithm (Goldman-Cecil Medicine, Fig. 227-2):

Clinical approach to investigation of hypercalcemia - Goldman-Cecil Medicine

Investigation Algorithm (Tietz Textbook of Laboratory Medicine, Fig. 54.6A):

Investigation algorithm for hypercalcemia - Tietz Laboratory Medicine

Investigation Algorithm (Harrison's Principles, Fig. 422-6):

Algorithm for evaluation of hypercalcemia based on duration and PTH - Harrison's

PTH-Based Differential Diagnosis

PTH Elevated (or Inappropriately Normal/Unsuppressed)

Condition	Key distinguishing features
Primary hyperparathyroidism (PHPT)	Chronic, usually asymptomatic; low-normal phosphate; solitary adenoma in 80-85%; ↑24h urine Ca; UCCR >0.02
Tertiary hyperparathyroidism	History of chronic renal failure (CKD); elevated creatinine; elevated phosphate; eGFR <30 mL/min
Familial Hypocalciuric Hypercalcemia (FHH)	Lifelong mild hypercalcaemia; family history; UCCR <0.01 (key distinguishing feature); 24h urine Ca <100 mg/day; CASR gene mutation
Lithium therapy	Drug history; lithium raises PTH set-point
MEN-1, MEN-2A	Family history; associated endocrine tumors (pituitary, pancreas, phaeochromocytoma, MTC)
Parathyroid carcinoma	Very high Ca (often >14 mg/dL), very high PTH, palpable neck mass
Ectopic PTH secretion by tumor	Extremely rare; confirmed by selective venous sampling

Distinguishing PHPT from FHH:

PHPT: UCCR typically >0.02 (urinary calcium/plasma calcium ÷ urinary creatinine/plasma creatinine)
FHH: UCCR typically <0.01
Genetic testing (CASR mutation) confirms FHH

PTH Suppressed (Low or Undetectable)

Condition	Key next tests
Malignancy (most common in inpatients)	Clinical evaluation; PTHrP assay (if >1.8 pmol/L, malignancy very likely); chest X-ray, CT, PET; SPEP for myeloma
Multiple myeloma	SPEP/UPEP, serum free light chains, bone marrow biopsy
Vitamin D intoxication	Drug/supplement history; elevated 25-OH vitamin D
Sarcoidosis / granulomatous disease	Elevated 1,25-(OH)₂D (calcitriol); ACE level; chest X-ray (bilateral hilar lymphadenopathy); tissue biopsy
Lymphoma	Elevated 1,25-(OH)₂D; imaging
Vitamin D-mediated (normal 25-OH-D)	Consider drugs, other endocrine disorders
Hyperthyroidism	TFTs (TSH, free T4)
Adrenal insufficiency	Morning cortisol, short Synacthen test
Immobilization	Clinical history; elevated bone turnover markers
Milk-alkali syndrome	History of high calcium + absorbable alkali intake
Vitamin A intoxication	Supplement history
Paget's disease	Elevated alkaline phosphatase; bone scan; immobilization precipitates hypercalcemia

Key Discriminating Tests - Summary

Test	When to order	Interpretation
Intact PTH	All patients	High = parathyroid cause; Low = non-parathyroid cause
PTHrP	PTH low, malignancy suspected	>1.8 pmol/L = humoral hypercalcemia of malignancy
24h urine calcium	PTH elevated	<100 mg/day or UCCR <0.01 → FHH
UCCR (urine Ca/Cr clearance ratio)	PTH elevated	<0.01 = FHH; >0.02 = PHPT
25-OH vitamin D	PTH suppressed, normal/low 1,25-D	Elevated = Vitamin D intoxication
1,25-(OH)₂D (calcitriol)	PTH suppressed, 25-OH-D normal	Elevated = sarcoid, lymphoma, granulomatous disease
ACE level	Granulomatous disease suspected	Elevated in sarcoidosis (not specific)
SPEP / serum free light chains	Anaemia, renal impairment, bone pain	Paraprotein = myeloma
TSH / free T4	Hyperthyroid features	Thyrotoxicosis
Short Synacthen test	Adrenal insufficiency suspected	Cortisol response
Serum phosphate	All patients	Low/normal in PHPT; high in renal failure and bone metastases
Chloride:phosphate ratio	PHPT workup	>33 in PHPT (hyperchloraemic metabolic acidosis)

Schwartz's Principles of Surgery, 11th Ed.; Harrison's 22nd Ed.

Duration of Hypercalcemia as a Diagnostic Clue

Duration	Most likely cause
Chronic (>1 year)	PHPT, FHH - malignancy very unlikely
Acute/subacute (weeks-months)	Malignancy (course is rapid; underlying tumor usually evident within months)
Incidental, truly asymptomatic	PHPT (>80% of PHPT patients in developed countries are asymptomatic at diagnosis)

Causes of Hypercalcemia - Full Classification

PTH-Mediated

Primary hyperparathyroidism (solitary adenoma 80-85%, multigland hyperplasia ~15%, carcinoma <1%)
Tertiary hyperparathyroidism (CKD)
MEN-1, MEN-2A
Familial hypocalciuric hypercalcemia (FHH) - CASR mutation
Lithium therapy
Parathyroid carcinoma

Malignancy-Related (PTH suppressed)

Humoral hypercalcaemia of malignancy (PTHrP secretion) - lung, breast, renal, head and neck SCC
Local osteolytic metastases - breast, multiple myeloma
1,25-(OH)₂D production by lymphoma
Ectopic PTH secretion (extremely rare)

Vitamin D-Mediated

Vitamin D₂/D₃ intoxication (supplements)
Sarcoidosis (pulmonary macrophage 1-hydroxylase activity not subject to feedback inhibition)
Other granulomatous diseases: TB, histoplasmosis, berylliosis
Lymphoma
Infantile hypercalcaemia (Williams syndrome - abnormal vitamin D sensitivity)

High Bone Turnover

Hyperthyroidism
Paget's disease with immobilization
Immobilization (in patients with pre-existing high bone turnover)

Drug-Related

Thiazide diuretics
Lithium
Vitamin D analogues
Vitamin A
Estrogen/antiestrogens (in breast cancer patients)
Milk-alkali syndrome (calcium carbonate + absorbable alkali)

Other Endocrine

Adrenal insufficiency / Addison's disease
Pheochromocytoma (some secrete PTHrP; MEN-2A association)
VIPoma (VIP-induced PTHrP)

Renal

Chronic renal failure → tertiary hyperparathyroidism
Post-renal transplant
Textbook of Family Medicine, 9th Ed.; Tietz Textbook of Laboratory Medicine, 7th Ed.; Goldman-Cecil Medicine

Severity Classification

Severity	Serum calcium	Clinical approach
Mild	<3.0 mmol/L (<12 mg/dL)	Usually asymptomatic; outpatient workup
Moderate	3.0-3.5 mmol/L (12-14 mg/dL)	Urgent if symptomatic; admit and treat
Severe / Hypercalcemic crisis	>3.5 mmol/L (>14 mg/dL)	Life-threatening; emergency treatment regardless of symptoms

Clinical Features ("Bones, Stones, Groans, Moans")

System	Features
Bones	Bone pain, osteitis fibrosa cystica (in severe PHPT), pathological fractures, subperiosteal resorption (PHPT)
Stones	Nephrolithiasis (calcium oxalate/phosphate), nephrocalcinosis
Groans	Nausea, vomiting, constipation, abdominal pain, peptic ulcers, pancreatitis
Moans	Depression, fatigue, weakness, confusion, obtundation, coma (in severe cases)
Cardiac	Shortened QT interval on ECG, arrhythmias
Renal	Polyuria, polydipsia (nephrogenic DI), dehydration, renal failure
Eyes	Band keratopathy (calcium deposits at corneal limbus)

Sources:

Harrison's Principles of Internal Medicine, 22nd Ed., Chapter 422 - Differential diagnosis and algorithm
Goldman-Cecil Medicine, Chapter 227 - Diagnosis and investigation algorithm
Tietz Textbook of Laboratory Medicine, 7th Ed., Chapter 54 - Laboratory investigation algorithms (Figs. 54.6A & B)
Schwartz's Principles of Surgery, 11th Ed., Chapter 38 - Biochemical studies, UCCR, FHH vs PHPT
Textbook of Family Medicine, 9th Ed. - Causes classification

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