Diagnostic Ultrasound - Abdomen and Pelvis
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Diagnostic Ultrasound - Abdomen and Pelvis

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Groin Hernia TERMINOLOGY Definitions • Hernia: Weakness or defect in fibromuscular wall with protrusion of organ or part of organ through defect ○ Groin hernias include indirect and direct inguinal hernias and femoral hernia • Reducible: Hernia recedes spontaneously or with external pressure (manual or transducer) • Incarcerated: Nonreducible • Strangulated: Compromised vascular supply of hernia contents IMAGING General Features • Location ○ Inguinal canal – ~ 4 cm long, ~ 1.2 cm above inguinal ligament, runs from anterior superior iliac spine to pubic tubercle □ Contains spermatic cord and ilioinguinal nerve in males, round ligament of uterus and ilioinguinal nerve in females ○ Femoral canal – ~ 2 cm long, just medial to femoral vein, deep and distal to inguinal ligament ○ Indirect inguinal hernia – Passes through deep inguinal ring, extends along inguinal canal, and emerges at superficial inguinal ring – Neck is lateral to inferior epigastric artery and above inguinal ligament – In males, usually extends along spermatic cord to scrotum – In females, may extend along round ligament to labia majora ○ Direct inguinal hernia – Passes through transversalis fascial defect in Hesselbach triangle – Protrudes anteriorly through abdominal wall – Wide neck medial to inferior epigastric artery and above inguinal ligament – Does not pass into spermatic cord and generally does not extend to scrotum ○ Femoral hernia – Passes through femoral canal into superomedial thigh – Narrow neck medial to femoral vein and below inguinal ligament ○ Double hernia – Simultaneous occurrence of direct and indirect inguinal hernia in same groin saddlebag hernia Ultrasonographic Findings • Grayscale ultrasound ○ Accurate at detecting hernia sac and contents, as well as fascial defect at rest or with provocative maneuvers – Increase in hernia size during cough, Valsalva maneuver, or standing ○ Contents – Omental fat: Echogenic without peristalsis – Bowel loops: Layers; "target" echo pattern with strong central echoes representing air or fluid in lumen □ Bowel peristalsis best assessed in real time – Fluid ○ Reducible hernia:Decrease in hernia size with decrease in intraabdominal pressure or application of external pressure to hernial sac with transducer ○ Nonobstructed hernia: Active peristalsis ± movement of intestinal contents ○ Strangulated hernia: Thickened sac, fluid, thickened bowel, echogenic fat ○ Obstructed hernia: Absence of peristalsis or hyperperistaltic loops in hernia, dilated/thick bowel loops in hernia sac or abdomen • Color Doppler ○ Helps identify inferior epigastric artery and its relationship to hernia sac – Differentiates direct and indirect inguinal hernias ○ Strangulated hernia: Absence of vascularity within bowel wall and mesentery is late sign CT and MR • Equivalent performance for most hernias but CT uses ionizing radiation • Obtained after nondiagnostic ultrasound; better for detecting alternative causes of symptoms or complicated hernias • Dynamic ultrasound more sensitive for smaller reducible hernias Radiographic Findings • Radiography ○ Gas-filled intestinal loops projecting over groin ○ ± small or large bowel obstruction • Herniography/peritoneography ○ Injection of soluble low-osmolar contrast medium into peritoneal cavity ○ Invasive but superior modality for occult inguinal hernias Imaging Recommendations • Best imaging tool ○ Ultrasound should be initial tool, accurate provided that strict systematic approach is used – Dynamic but operator dependent – 97% sensitivity, 85% specificity, and 93% positive predictive value for diagnosis of groin hernia – Lower accuracy for determining type of hernia (indirect inguinal, direct inguinal, femoral) – Pure fat hernia most difficult to diagnose ○ CT or MR if ultrasound is equivocal • Protocol advice ○ High-resolution linear transducer ○ Start lateral to rectus muscle and identify inferior epigastric artery (IEA) – Follow IEA down to origin on external iliac artery; this is deep inguinal ring ○ Orient transducer parallel to inguinal ligament ○ Scan caudad over femoral vessels, look for femoral hernia medially at saphenofemoral junction ○ Scan cephalad, find origin of inferior epigastric artery off medial femoral artery, look for indirect inguinal hernia Diagnoses: Abdominal Wall/Peritoneal Cavity 619

Groin Hernia Diagnoses: Abdominal Wall/Peritoneal Cavity ○ Scan medially for superficial ring and look for direct inguinal hernia ○ At each area, examine at rest and during Valsalva maneuver for presence of hernia or laxity ○ Examine other side if hernia found, examine sites of tenderness ○ Cine clips strongly advised ○ Repeat with patient standing, more sensitive for fluid in hernia DIFFERENTIAL DIAGNOSIS Lipoma of Spermatic Cord • No change with Valsalva maneuver, not reducible • Usually no deep extension into peritoneal cavity Encysted Hydrocele Canal of Nück • Processus vaginalis extends from peritoneal cavity to scrotum in embryo ○ Normally obliterates in cord while scrotal component persists as tunica vaginalis ○ Failure of obliteration leads to fluid distension within cord, known as encysted hydrocele canal of Nück – Filled with anechoic fluid, no change with Valsalva maneuver, not reducible – No deep extension into peritoneal cavity Inguinal Canal Lesions • Benign and malignant tumors: Neurofibroma, desmoid, metastases, lymphadenopathy, lymphoma, sarcomas • Undescended testis • Miscellaneous: Varicocele, abscess, hematoma, granuloma, scar PATHOLOGY General Features • Etiology ○ Multifactorial – Chronic: Increased intraabdominal pressure from abdominal distension (ascites) □ Weak abdominal musculature: Chronic cough, prostatism, constipation, manual labor, pregnancy, steroids, collagen abnormality, smoking – Acute: Sudden severe increase in intraabdominal pressure ○ Indirect inguinal hernia: Congenital due to persistence of processus vaginalis in infants and children Gross Pathologic & Surgical Features • Sac contents: Commonly omentum, ascites, small bowel, or mobile colon segments (sigmoid, cecum, appendix), rarely bladder, ovary ○ Littre hernia: Meckel diverticulum in sac ○ Richter hernia: Only portion of bowel circumference (antimesenteric portion) in sac CLINICAL ISSUES Presentation • Most common signs/symptoms ○ Groin lump or discomfort with positive cough impulse (allows clinical diagnosis) – Continuous or intermittent • Other signs/symptoms ○ Features of intestinal obstruction Demographics • Age ○ Indirect inguinal hernia tend to occur in young to middleaged individuals ○ Prevalence of direct inguinal hernia increases with increasing age ○ Femoral hernia is more common in middle-aged to elderly individuals • Gender ○ Indirect inguinal hernia is 5-10x more common in males ○ Direct inguinal hernia nearly always occurs in males ○ Femoral hernia is more common in females – However, indirect inguinal hernia is most common hernia in females • Epidemiology ○ Hernia repair is most common surgical procedure in US ○ 5% of males develop groin hernia ○ 75% of all hernias inguinal, indirect to direct 5:1 ○ 10-15% femoral ○ Inguinal hernia in children is always result of patent processus vaginalis and is thus indirect hernia extending to scrotal sac Natural History & Prognosis • Recurrence rate after repair: 1-15% ○ Direct inguinal hernia may develop after repair of indirect inguinal hernia • Complications: Obstruction, strangulation ○ Indirect inguinal hernias account for 15% of intestinal obstruction cases ○ Obstruction or strangulation more common with femoral hernias due to narrow neck Treatment • Laparoscopic or open hernia repair DIAGNOSTIC CHECKLIST Consider • Relation of hernia neck to inferior epigastric artery for inguinal hernias • Femoral hernia: Below inguinal ligament SELECTED REFERENCES 1. Arend CF: Static and dynamic sonography for diagnosis of abdominal wall hernias. J Ultrasound Med. 32(7):1251-9, 2013 2. Jain N et al: Ultrasound of the abdominal wall: what lies beneath? Clin Radiol. 68(1):85-93, 2013 3. Robinson A et al: Meta-analysis of sonography in the diagnosis of inguinal hernias. J Ultrasound Med. 32(2):339-46, 2013 4. Stavros AT et al: Dynamic ultrasound of hernias of the groin and anterior abdominal wall. Ultrasound Q. 26(3):135-69, 2010 5. Bhosale PR et al: The inguinal canal: anatomy and imaging features of common and uncommon masses. Radiographics. 28(3):819-35; quiz 913, 2008 620

Groin Hernia<br />

TERMINOLOGY<br />

Definitions<br />

• Hernia: Weakness or defect in fibromuscular wall with<br />

protrusion of organ or part of organ through defect<br />

○ Groin hernias include indirect <strong>and</strong> direct inguinal hernias<br />

<strong>and</strong> femoral hernia<br />

• Reducible: Hernia recedes spontaneously or with external<br />

pressure (manual or transducer)<br />

• Incarcerated: Nonreducible<br />

• Strangulated: Compromised vascular supply of hernia<br />

contents<br />

IMAGING<br />

General Features<br />

• Location<br />

○ Inguinal canal<br />

– ~ 4 cm long, ~ 1.2 cm above inguinal ligament, runs<br />

from anterior superior iliac spine to pubic tubercle<br />

□ Contains spermatic cord <strong>and</strong> ilioinguinal nerve in<br />

males, round ligament of uterus <strong>and</strong> ilioinguinal<br />

nerve in females<br />

○ Femoral canal<br />

– ~ 2 cm long, just medial to femoral vein, deep <strong>and</strong><br />

distal to inguinal ligament<br />

○ Indirect inguinal hernia<br />

– Passes through deep inguinal ring, extends along<br />

inguinal canal, <strong>and</strong> emerges at superficial inguinal ring<br />

– Neck is lateral to inferior epigastric artery <strong>and</strong> above<br />

inguinal ligament<br />

– In males, usually extends along spermatic cord to<br />

scrotum<br />

– In females, may extend along round ligament to labia<br />

majora<br />

○ Direct inguinal hernia<br />

– Passes through transversalis fascial defect in<br />

Hesselbach triangle<br />

– Protrudes anteriorly through abdominal wall<br />

– Wide neck medial to inferior epigastric artery <strong>and</strong><br />

above inguinal ligament<br />

– Does not pass into spermatic cord <strong>and</strong> generally does<br />

not extend to scrotum<br />

○ Femoral hernia<br />

– Passes through femoral canal into superomedial<br />

thigh<br />

– Narrow neck medial to femoral vein <strong>and</strong> below<br />

inguinal ligament<br />

○ Double hernia<br />

– Simultaneous occurrence of direct <strong>and</strong> indirect<br />

inguinal hernia in same groin saddlebag hernia<br />

Ultrasonographic Findings<br />

• Grayscale ultrasound<br />

○ Accurate at detecting hernia sac <strong>and</strong> contents, as well as<br />

fascial defect at rest or with provocative maneuvers<br />

– Increase in hernia size during cough, Valsalva<br />

maneuver, or st<strong>and</strong>ing<br />

○ Contents<br />

– Omental fat: Echogenic without peristalsis<br />

– Bowel loops: Layers; "target" echo pattern with strong<br />

central echoes representing air or fluid in lumen<br />

□ Bowel peristalsis best assessed in real time<br />

– Fluid<br />

○ Reducible hernia:Decrease in hernia size with decrease<br />

in intraabdominal pressure or application of external<br />

pressure to hernial sac with transducer<br />

○ Nonobstructed hernia: Active peristalsis ± movement of<br />

intestinal contents<br />

○ Strangulated hernia: Thickened sac, fluid, thickened<br />

bowel, echogenic fat<br />

○ Obstructed hernia: Absence of peristalsis or<br />

hyperperistaltic loops in hernia, dilated/thick bowel loops<br />

in hernia sac or abdomen<br />

• Color Doppler<br />

○ Helps identify inferior epigastric artery <strong>and</strong> its<br />

relationship to hernia sac<br />

– Differentiates direct <strong>and</strong> indirect inguinal hernias<br />

○ Strangulated hernia: Absence of vascularity within bowel<br />

wall <strong>and</strong> mesentery is late sign<br />

CT <strong>and</strong> MR<br />

• Equivalent performance for most hernias but CT uses<br />

ionizing radiation<br />

• Obtained after nondiagnostic ultrasound; better for<br />

detecting alternative causes of symptoms or complicated<br />

hernias<br />

• Dynamic ultrasound more sensitive for smaller reducible<br />

hernias<br />

Radiographic Findings<br />

• Radiography<br />

○ Gas-filled intestinal loops projecting over groin<br />

○ ± small or large bowel obstruction<br />

• Herniography/peritoneography<br />

○ Injection of soluble low-osmolar contrast medium into<br />

peritoneal cavity<br />

○ Invasive but superior modality for occult inguinal hernias<br />

Imaging Recommendations<br />

• Best imaging tool<br />

○ <strong>Ultrasound</strong> should be initial tool, accurate provided that<br />

strict systematic approach is used<br />

– Dynamic but operator dependent<br />

– 97% sensitivity, 85% specificity, <strong>and</strong> 93% positive<br />

predictive value for diagnosis of groin hernia<br />

– Lower accuracy for determining type of hernia<br />

(indirect inguinal, direct inguinal, femoral)<br />

– Pure fat hernia most difficult to diagnose<br />

○ CT or MR if ultrasound is equivocal<br />

• Protocol advice<br />

○ High-resolution linear transducer<br />

○ Start lateral to rectus muscle <strong>and</strong> identify inferior<br />

epigastric artery (IEA)<br />

– Follow IEA down to origin on external iliac artery; this<br />

is deep inguinal ring<br />

○ Orient transducer parallel to inguinal ligament<br />

○ Scan caudad over femoral vessels, look for femoral<br />

hernia medially at saphenofemoral junction<br />

○ Scan cephalad, find origin of inferior epigastric artery off<br />

medial femoral artery, look for indirect inguinal hernia<br />

Diagnoses: Abdominal Wall/Peritoneal Cavity<br />

619

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