Approach

Inguinal hernias have 4 basic clinical presentations:

  • Asymptomatic groin swelling or bulge

  • Symptomatic groin swelling or bulge

  • Inguinoscrotal swelling

  • Acute abdomen (rare).

History and clinical evaluation

It is critical to obtain a clear, detailed history of the symptoms when evaluating a patient with groin pain attributed to possible inguinal hernia.[45] Pain associated with a hernia is felt only when the hernia is bulging, unlike pain from a groin injury, which is continuous, aggravated by motion, and not associated with a bulge.

The patient may report a dragging sensation in the groin or an intermittent bulge that disappears when lying flat. If the hernia is obstructed or strangulated, the patient may present with severe abdominal pain, nausea and vomiting. Clinically, hernia associated with an acute abdomen may be irreducible, tender, with absent bowel sounds. Such a patient is often volume depleted with low urine output and occasional altered mental status.

Most hernias can be detected by simply observing an asymmetry in the groin region with the patient standing before you. The internal ring can be located by placing fingers on the anterior superior iliac spine and thumb over the spot halfway between the iliac spine and the pubis. A bulge in the inguinal canal can be detected by gentle palpation with the thumb over the internal and external ring areas. Alternatively, in the absence of a visible or easily palpable bulge, a bulge may be palpated at the external ring by invaginating the upper scrotum (in men) and asking the patient to cough or perform a Valsalva manoeuvre (forced expiration through a closed airway). Older literature commonly states that if an 'impulse' is felt using this method then this would indicate a hernia; however, as a clinical sign, this is poorly defined, often leads to false positives, and has little clinical significance, especially in patients with groin pain. Furthermore, invaginating the scrotum and inserting a finger into the external ring can be uncomfortable for patients (and, of course, impossible in women). Palpation in this way, however, may be useful in very obese men (class III obesity, BMI of 40 or above).

An indirect hernia may theoretically be controlled by applying occlusive pressure at the mid-point of the inguinal ligament, whereas a direct hernia is not affected by this manoeuvre. However, discrimination between direct and indirect inguinal hernia by physical examination is not very accurate and should not affect decision-making with regard to treatment decisions.[46][47][48]

Investigation

Diagnosis is almost always clinical, based on physical examination.[11] There is no requirement for imaging for a clinically obvious inguinal hernia. Radiographic imaging may be helpful if there is diagnostic uncertainty (e.g., in a patient with class II or III obesity which makes physical examination difficult or with unexplained groin pain).

If imaging is required, an ultrasound scan of the groin should be the initial investigation.[49] However, false-positive tests are common in patients with atypical groin pain, and very small, clinically insignificant or 'fat containing' hernias are often detected.[50][51]

A computed tomography (CT) scan of the groin is indicated if the ultrasound scan is negative and clinical suspicion is high. Although a positive finding of inguinal hernia on a CT scan is reliable, a negative finding does not exclude the diagnosis. The inguinal canal almost always contains fat alongside the cord structures; therefore, clinical correlation may be required to differentiate true hernias from asymptomatic fat-containing hernias, which may appear as incidental findings on a CT scan.[52] Administering an oral contrast agent and performing a Valsalva manoeuvre during the scan can aid in diagnosis. CT abdomen and pelvis has demonstrated sensitivities of 54% to 80% and specificities of 25% to 65%.[53][54]

Magnetic resonance imaging (MRI) is used in patients with clinically uncertain symptoms. In a retrospective study of patients with suspected occult inguinal hernia, MRI demonstrated sensitivity of 91% and specificity of 92%.[54]

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