Role of USG Xray and Per rectal examination for General surgeon with viva questions with reasoning and answer

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Role of USG, X-Ray, and Per Rectal Examination for the General Surgeon

A. ULTRASONOGRAPHY (USG)

Principles & Physical Basis

Ultrasound uses high-frequency sound waves (2-15 MHz) emitted from piezoelectric crystals in the transducer probe. Different tissues have variable acoustic impedance - high-density tissues are hyperechoic (bright), fluid is anechoic (black), and soft tissue is hypoechoic (grey). No ionizing radiation is involved.

Transducer types relevant to surgeons:

Curvilinear (3-5 MHz): Abdominal organs, deep structures, FAST exam
Phased array (3-5 MHz): Cardiac windows, between ribs
Linear/vascular (7-12 MHz): Superficial structures, veins, thyroid, breast, hernias

Roles of USG in General Surgery

1. FAST Exam (Focused Assessment with Sonography in Trauma)

The FAST exam became standard of care after ACS endorsement in the mid-1990s and is incorporated into ATLS.

Four windows of FAST:

Window	Location	Looking For
Pericardial	Subxiphoid	Haemopericardium
Right upper quadrant (Morison's pouch)	Hepatorenal space	Free fluid
Left upper quadrant (splenorenal space)	Splenorenal recess	Free fluid
Pelvis (Pouch of Douglas)	Suprapubic	Free fluid

E-FAST adds bilateral thoracic windows to detect pneumothorax (loss of pleural sliding sign) and haemothorax.

Clinical algorithm:

Free fluid + haemodynamically UNSTABLE → immediate laparotomy
Free fluid + haemodynamically STABLE → proceed to CT for organ characterization
Negative FAST + high suspicion → repeat scan (organized haematoma may be isoechoic initially)

Advantages of FAST:

Rapid (3-4 minutes)
Non-invasive, repeatable
Replaces diagnostic peritoneal lavage (DPL)
Bedside, no radiation

Limitations of FAST:

Cannot penetrate bowel gas
Reduced accuracy in obesity
Cannot characterize specific organ injury
Cannot detect retroperitoneal haematomas reliably
Early clotted blood may be isoechoic (false negative)

2. USG in Biliary Disease (Gold Standard)

USG is the first-line and gold standard investigation for:

Cholelithiasis: Hyperechoic stones with posterior acoustic shadowing, sensitivity >95%
Acute cholecystitis: Gallbladder wall thickening (>3 mm), pericholecystic fluid, sonographic Murphy's sign, impacted stone
Biliary dilation: CBD >6 mm (>8 mm post-cholecystectomy suggests obstruction)
Cholangitis: Ductal dilation with clinical triad (Charcot's triad)

3. USG in Appendicitis

Non-compressible, aperistaltic tubular structure >6 mm diameter
Target sign (on cross-section)
Periappendiceal free fluid
Limited by obesity and bowel gas; CT preferred when inconclusive

4. USG in Abdominal Aortic Aneurysm (AAA)

Aortic diameter >3 cm = AAA; >5.5 cm = surgical threshold
Used for screening (UK national AAA screening programme - 65-year-old males)
Bedside USG in shocked patient with suspected AAA: if positive → immediate surgical intervention (do NOT send to CT if unstable)

5. USG-Guided Interventions

Ultrasound-guided central line insertion (IJV, subclavian)
Drainage of collections (abscess, haematoma, biloma)
Percutaneous cholecystostomy
Biopsy of liver lesions, lymph nodes, thyroid

6. Other Surgical Uses

Thyroid nodules (Doppler, FNAC guidance)
Breast lumps (solid vs. cystic; FNAC/core biopsy guidance)
Inguinal hernia (reduces vs. irreducible; Doppler for blood flow in testes)
Testicular torsion (absent blood flow on Doppler)
Soft tissue lumps (lipoma vs. epidermal cyst vs. malignant)
Varicose veins (duplex Doppler: saphenofemoral junction, perforators)

B. PLAIN X-RAY (Radiograph) in Surgery

Types Relevant to Surgeons

View	Clinical Use
Erect CXR	Free gas under diaphragm (perforation), pleural effusion, lung metastases
Supine AXR	Bowel gas pattern, obstruction
Erect AXR	Air-fluid levels (SBO), free gas
Lateral decubitus AXR	When patient cannot stand erect; free gas

Specific X-Ray Findings and Surgical Significance

1. Pneumoperitoneum (Perforated Viscus)

Erect CXR: Free gas under the right hemidiaphragm (crescent of gas)
Requires as little as 1 mL of free air to be detectable
Classic cause: Perforated peptic ulcer (most common), perforated appendix, perforated diverticulitis
Management: Emergency laparotomy / laparoscopy

2. Small Bowel Obstruction (SBO)

Supine AXR: Central dilated loops of small bowel (valvulae conniventes = Kerckring's folds cross the entire lumen)
Erect AXR: Multiple air-fluid levels at different heights ("step-ladder pattern")
Paucity of colonic gas
Small bowel >3 cm = dilated
Allows early NGT placement before CT to reduce aspiration risk

3. Large Bowel Obstruction (LBO)

Peripheral frame of dilated colon with haustral folds (haustra do NOT cross entire lumen - unlike valvulae conniventes)
Caecum >9 cm = risk of perforation
Collapsed small bowel if ileocaecal valve is competent (closed loop)

4. Sigmoid Volvulus

"Coffee bean sign" / "Bent inner tube sign": inverted U-shaped dilated loop of sigmoid pointing to right upper quadrant
Apex points away from the site of obstruction
Immediate management: Flexible sigmoidoscopy for decompression

5. Caecal Volvulus

"Comma-shaped" or "kidney-shaped" loop in the left upper quadrant or mid-abdomen
Less common; requires surgery

6. Paralytic Ileus

Gas throughout both small and large bowel without obstruction
No air-fluid levels (unlike mechanical obstruction)
Post-operative, metabolic (hypokalaemia, hypothyroidism)

7. Toxic Megacolon (in Inflammatory Bowel Disease)

Transverse colon >6 cm
Mucosal islands ("thumb-printing") in the dilated colon
Surgical emergency

8. Nephrolithiasis / Ureteric Calculi (KUB Film)

90% of renal stones are radio-opaque (calcium oxalate/phosphate)
Uric acid and cystine stones are radiolucent
Staghorn calculus = occupies full pelvi-calyceal system

9. Chest X-Ray in Surgery (Pre-op, Post-op)

Pneumothorax: Absent lung markings with visible pleural line
Haemothorax: Opacification in chest trauma
Lung metastases: "Cannonball" secondaries (renal cell, thyroid, sarcoma)
Mediastinal widening: Aortic dissection, superior mediastinal mass
Foreign bodies: Swallowed or implanted
Post-op complications: Surgical emphysema, atelectasis, pleural effusion

10. Fractures with Surgical Implications

Rib fractures: 3 or more = flail chest; below 8th rib = suspect liver/spleen injury
Pelvic fractures: Associated massive retroperitoneal haemorrhage; Malgaigne fracture (vertical shear = life-threatening)
Cervical spine: Cleared before proceeding in trauma

C. PER RECTAL (PR) EXAMINATION

Importance in Surgery

"It is criminal not to perform rectal examination in patients with any rectal complaint. About 90% of rectal cancers can be felt by digital examination." - S. Das, Manual of Clinical Surgery

Positions for PR Examination

Position	Clinical Situation
Left lateral (Sims)	Standard - most comfortable, best for routine DRE and anoscopy
Lithotomy	Preferred for bimanual examination and EUA
Knee-chest (genupectoral)	Better view of anorectal junction
Supine	Bedridden patients, trauma

Systematic Approach to PR Examination

Step 1: INSPECTION (before insertion)

Skin tags, external piles, fissure (10 o'clock or 2 o'clock position if posterior midline = primary fissure; other positions = secondary - suspect Crohn's, TB, syphilis)
Fistulous openings (Goodsall's rule)
Rectal prolapse (ask patient to strain)
Condylomata acuminata
Perianal haematoma (3 o'clock / 9 o'clock)

Step 2: DIGITAL EXAMINATION (PR)

Always use gloved, lubricated index finger.

A. Within the Lumen:

Faeces - character (hard, soft, blood-stained)
Polyps
Carcinoma: Hard, irregular, ulcerated edge; determine % circumference involved; fixed vs. mobile (mobility preserved while within fascia propria of rectum)
Stricture: Benign = clean-cut hole (diaphragm-like); Malignant = hard, irregular, ulcerated

B. Within the Wall:

Tumours (intramural)
Granular areas (proctitis, Crohn's)

C. Outside the Rectum (most important clinically):

Anteriorly (male):

Prostate: Normal = firm, rubbery, bilobed, smooth surface, central sulcus; BPH = enlarged, smooth, rubbery, central sulcus preserved; Carcinoma = hard, nodular, loss of central sulcus, may be fixed; Prostatitis = tender, boggy
Seminal vesicles: Not normally palpable; if felt = carcinoma or infection
Base of bladder

Anteriorly (female):

Cervix: Normal = firm, round, transverse slit; carcinoma = hard, irregular
Uterus: Anteverted/retroverted position, fibroids
Pouch of Douglas (recto-uterine/recto-vesical): Blood (haemoperitoneum), pus (pelvic abscess/appendix), malignant deposit (Blumer's shelf/rectal shelf = secondary deposits from stomach/ovary), tumour of sigmoid

Laterally:

Pelvic appendix: Tenderness in pelvic appendicitis (may have no abdominal guarding - "silent appendix")
Ischio-rectal abscess: Tender tense swelling
Pelvic sidewall / ureters / internal iliac vessels
Ovarian cysts, fallopian tubes (salpingitis, ectopic pregnancy)

Posteriorly:

Hollow of sacrum and coccyx
Coccydynia: Abnormal mobility and tenderness (bidigital - finger inside + thumb over coccyx)
Sacrococcygeal teratoma, post-anal dermoid

Step 3: WITHDRAWAL AND EXAMINATION OF GLOVE

Always examine the glove on withdrawal:

Bright red blood: Haemorrhoids, fissure, rectal polyp/carcinoma
Dark blood / mucus: Carcinoma, IBD, intussusception (red-currant jelly)
Pus: Abscess, Crohn's, proctitis
Melaena: Upper GI bleed

Key Surgical Conditions Diagnosed on PR

Condition	PR Finding
Carcinoma rectum	Hard, irregular ulcerated mass; fixity determines resectability
BPH	Smooth, rubbery enlarged prostate, median sulcus present
Carcinoma prostate	Hard, craggy, nodular; loss of median sulcus; may be fixed
Pelvic appendicitis	Right lateral tenderness, no abdominal guarding
Blumer's shelf	Hard nodular deposits in pouch of Douglas (stomach/ovary Ca metastases)
Pelvic abscess	Boggy tender mass anteriorly in pouch of Douglas
Haemoperitoneum	Bogginess/fullness in pouch of Douglas
Anal fissure	Tenderness; examination often not possible without anaesthesia
Pelvic fracture	Tenderness, bony crepitus, displaced prostate (high-riding in urethral injury)
Anorectal abscess	Ischio-rectal = lateral bulging tender swelling

"Blumer's Shelf" - Classic Surgical Sign

Palpable hard nodular mass in the pouch of Douglas due to transcoelomic metastatic deposits from gastric carcinoma or ovarian carcinoma. Sometimes called the "rectal shelf." A finding of Blumer's shelf = inoperable disease (M1).

High-Riding Prostate in Urethral Injury

In pelvic fracture with urethral disruption, the prostate is "floated up" by haematoma and cannot be palpated in its normal position. Do NOT attempt urethral catheterisation - perform suprapubic cystostomy.

VIVA QUESTIONS WITH REASONING AND ANSWERS

SECTION 1: USG VIVA

Q1. What is the FAST exam? What are the four windows and what do you look for in each?

A: FAST = Focused Assessment with Sonography in Trauma. It is a bedside, rapid (3-4 minutes), non-invasive tool to detect free fluid or haemopericardium in trauma. The four windows are:

Subxiphoid/Pericardial - haemopericardium
Right upper quadrant (Morison's pouch) - fluid between liver and right kidney
Left upper quadrant (splenorenal space) - fluid between spleen and left kidney
Pelvis (suprapubic/pouch of Douglas) - pelvic free fluid

Reasoning: These are the dependent spaces where free blood collects first in a supine patient.

Q2. FAST is positive with free fluid. What determines your next step?

A: Haemodynamic status:

Unstable → immediate laparotomy/laparoscopy (no time for CT)
Stable → CT abdomen with contrast for organ characterization and further evaluation

Reasoning: In an unstable patient, delay for CT scan = death. The FAST gives just enough information (free blood = source of haemorrhage = abdomen) to take the patient to theatre.

Q3. What are the limitations of FAST?

Cannot penetrate bowel gas (obscures views)
Reduced sensitivity in obese patients (poor wave penetration)
Cannot identify retroperitoneal haematoma reliably
Early clotting blood may be isoechoic to liver/spleen (false negative)
Operator-dependent
Cannot identify specific organ injury
Misses isolated solid organ injury without free fluid
Sensitivity only ~70-80% for haemoperitoneum

Q4. Why is USG the gold standard for cholelithiasis and not CT?

A: Ultrasound identifies gallstones as hyperechoic structures with posterior acoustic shadowing with >95% sensitivity, better than CT. Moreover, most gallstones are cholesterol-based and have similar density to bile on CT (isodense), making them invisible. Ultrasound also has no radiation, is cheap, and can simultaneously assess CBD calibre.

Q5. A patient presents with a pulsatile abdominal mass and is in shock. What is the role of USG?

A: Bedside POCUS (point-of-care USG) to measure aortic diameter. If >5.5 cm = ruptured/leaking AAA. In a haemodynamically unstable patient with suspected ruptured AAA, a positive POCUS (aorta >5.5 cm) = immediate transfer to operating theatre. Do NOT perform CT - this wastes precious time and the patient may die on the table. USG takes 2 minutes and is sufficient to make this life-saving decision.

Q6. What is E-FAST? When would you use it?

A: Extended FAST adds bilateral thoracic windows to the standard FAST. It detects:

Pneumothorax: Loss of "lung sliding" sign on pleural line
Haemothorax: Anechoic fluid above diaphragm
Haemopericardium: Fluid around pericardium

Used in penetrating chest trauma, polytrauma, blunt chest injury - any setting where pneumothorax or haemothorax is suspected alongside abdominal injury.

Q7. What is sonographic Murphy's sign?

A: Maximum tenderness elicited by the ultrasound probe placed directly over the gallbladder (rather than the examiner's hand). This sign is highly specific (>90%) for acute cholecystitis. It is more reliable than clinical Murphy's sign because it confirms that the tenderness is directly over the gallbladder, not an adjacent structure.

SECTION 2: X-RAY VIVA

Q8. Where does free gas appear on an erect CXR and what does it signify?

A: Free gas appears as a crescent-shaped translucency under the right hemidiaphragm (right side preferred because the liver acts as a contrast backdrop; left side obscured by gastric gas bubble). It signifies perforation of a hollow viscus - peptic ulcer (most common), perforated appendix, perforated diverticulum, or traumatic bowel injury. Requires emergency surgical intervention.

Q9. How do you differentiate small bowel from large bowel on plain AXR?

Feature	Small Bowel	Large Bowel
Location	Central	Peripheral (frame-like)
Mucosal folds	Valvulae conniventes (cross the ENTIRE lumen)	Haustra (do NOT cross entire lumen)
Diameter	>3 cm = dilated	>6 cm transverse, >9 cm caecum = dilated
Gas in rectum	Present (partial obstruction)	Absent below obstruction

Q10. What is the "coffee bean sign"? What is its surgical significance?

A: The coffee bean (or "bent inner tube") sign is a large inverted-U shaped dilated loop of sigmoid colon on AXR, with the apex pointing towards the right upper quadrant. It is pathognomonic of sigmoid volvulus. Surgical significance: If no signs of perforation, attempt decompression with a flatus tube/flexible sigmoidoscopy. If peritonism or peritonitis is present = emergency resection (Hartmann's procedure). High recurrence rate (~90%) after conservative treatment - elective sigmoid resection should be offered.

Q11. A patient with severe abdominal pain has a normal erect CXR. Does this exclude perforation?

A: No. Up to 10-20% of perforations show no free gas on erect CXR because:

Insufficient air has escaped (sealed perforations)
Patient cannot sit erect
Omentum has sealed the perforation
Film quality is poor In such cases, a CT abdomen is the investigation of choice as it detects even small amounts of free gas. Alternatively, a left lateral decubitus AXR may show free gas if the patient cannot stand.

Q12. What is toxic megacolon? What is the X-ray finding?

A: Toxic megacolon is a life-threatening complication of IBD (usually UC, less often Crohn's), C. difficile, or ischaemic colitis. AXR shows transverse colon >6 cm in diameter with "thumb-printing" (mucosal oedema creating scalloped indentations). Associated features: loss of haustral pattern, mucosal islands. Management: urgent surgical opinion, IV fluids, steroids, antibiotics; if no improvement in 24-72 hours = colectomy.

Q13. What are the X-ray features of intestinal obstruction vs. paralytic ileus?

Feature	Mechanical Obstruction	Paralytic Ileus
Gas distribution	Dilated bowel up to obstruction, collapsed beyond	Gas throughout colon AND small bowel
Air-fluid levels	Multiple, at DIFFERENT heights	Absent or uniform height
Peristalsis	Increased (tinkling) then absent	Absent (silent abdomen)
Clinical	Colicky pain	Constant distension, no pain

SECTION 3: PER RECTAL EXAMINATION VIVA

Q14. What is the reach of the examining finger and what structures can be felt?

A: The index finger reaches approximately 7-8 cm into the rectum. The floor of the pouch of Douglas can be reached - about 1 inch above the floor in females, half that in males.

Structures palpable anteriorly:

Male: Prostate, seminal vesicles (if enlarged), base of bladder, floor of recto-vesical pouch
Female: Cervix, uterus (retroverted), vaginal wall, floor of pouch of Douglas

Q15. What is Blumer's shelf? What is its clinical significance?

A: Blumer's shelf is a hard, nodular, shelf-like deposit felt in the floor of the pouch of Douglas on PR examination. It represents transcoelomic (peritoneal) metastatic spread, most commonly from carcinoma of the stomach or carcinoma of the ovary. Its presence signifies inoperable/stage IV disease (M1 = peritoneal deposits). Named after George Blumer (American gastroenterologist).

Q16. How do you differentiate benign from malignant stricture of the rectum on PR?

Benign stricture: Feels like a diaphragm with a clean-cut, smooth central hole; mucosa over it may be normal; rubbery in feel (LGV stricture is tubular and rubbery)
Malignant stricture: Hard, irregular, often ulcerated; friable; finger may be bloodstained on withdrawal

Q17. A patient with acute abdomen has no tenderness on abdominal palpation but maximal tenderness on PR. What is the diagnosis and why?

A: Pelvic appendicitis. When the appendix lies in the pelvis, it is below the peritoneal reflection and inflammation does not cause direct anterior abdominal wall tenderness. However, the inflamed appendix is accessible to the examining finger via the right lateral wall of the rectum, eliciting maximal tenderness. This is the "silent appendix" of pelvic appendicitis - a clinical trap if PR examination is omitted.

"It is criminal not to perform rectal examination" - this scenario is the classic reason why.

Q18. What does a "high-riding prostate" on PR signify? What should you NOT do?

A: A prostate that is not palpable in its normal position (floated up, "high-riding") in a patient with pelvic fracture and inability to void indicates a posterior urethral disruption (rupture of membranous urethra at prostato-membranous junction). The prostate is displaced upward by a pelvic haematoma.

Do NOT pass a urethral catheter - this may:

Introduce infection
Convert a partial tear to a complete rupture
Create a false passage

Management: Suprapubic cystostomy; formal urological repair later.

Q19. What is Goodsall's rule?

A: Goodsall's rule predicts the internal opening of an anal fistula:

Posterior fistulae (posterior to a transverse line through the anus): curved track that opens into the posterior midline of the anal canal, regardless of where the external opening is
Anterior fistulae (anterior to the transverse line): direct radial track to the nearest point of the anal canal
Exception: Anterior fistulae with external opening >3 cm from the anal margin may behave like posterior fistulae (horseshoe pattern)

Reasoning: This is important before fistulotomy to predict where the internal opening is (if you lay open the wrong tract, you can cause incontinence).

Q20. What is the significance of anal tone on PR examination?

Increased tone (hypertonia): Chronic anal fissure (spasm of internal sphincter), pain, anal stenosis
Decreased tone / patulous anus: Rectal prolapse (stretch injury to pudendal nerve), faecal incontinence, spinal cord injury (S2-S4), cauda equina syndrome
Absent tone: Paraplegia, complete sacral nerve damage
Assessment: Resting tone (internal sphincter = autonomic) vs. squeeze pressure (external sphincter = voluntary, pudendal nerve S2-S4)

This is critical before any sphincter-involving anorectal surgery (fistulotomy, lateral internal sphincterotomy) to assess baseline continence risk.

SUMMARY TABLE: Quick Revision

Investigation	Best For	Key Finding	Surgical Action
USG (FAST)	Trauma	Free fluid in Morison's/POD	Laparotomy if unstable
USG	Gallstones	Acoustic shadow	Cholecystectomy
USG	AAA	Aorta >5.5 cm	Emergency OR if unstable
Erect CXR	Perforation	Sub-diaphragmatic gas	Emergency laparotomy
AXR Erect	SBO	Step-ladder air-fluid levels	NGT, IV fluids, surgery if needed
AXR Supine	Sigmoid volvulus	Coffee bean sign	Sigmoidoscopy/Hartmann's
PR exam	Rectal Ca	Hard irregular mass	Staging, anterior resection vs. APR
PR exam	Pelvic appendicitis	Right lateral tenderness	Appendicectomy
PR exam	Blumer's shelf	Hard deposits in POD	Staging → palliation
PR exam	Urethral injury	High-riding prostate	Suprapubic cystostomy

Sources: Bailey & Love's Short Practice of Surgery 28th Ed.; S. Das Manual of Clinical Surgery 13th Ed.; Sabiston Textbook of Surgery; Fischer's Mastery of Surgery 8th Ed.; Gray's Anatomy for Students; Roberts & Hedges' Clinical Procedures in Emergency Medicine.

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