Approach to postoperative abdominal pain: Clinical sciences

Postoperative abdominal pain is commonly reported by patients after surgery. There are many causes, some even life-threatening, but they can all be summed up into three categories: disruption of normal healing, infection, or other benign physiologic processes. Abdominal pain can be superficial, or limited to the abdominal wall; or it can be deep, involving organ space.

The first step in evaluating a patient with signs and symptoms suggestive of postoperative abdominal pain is to perform the ABCDE assessment to determine if the patient is stable or unstable. If the patient is unstable, start acute management before doing any diagnostic workup. This means that you might need to stabilize their airway, provide supplemental oxygen, establish IV access, and consider starting IV fluids, while continuously monitoring their vitals.

Some important examples that can cause a patient to be unstable in the postoperative period include acute abdomen, caused by free air or diffuse fluid spillage; as well as vascular rupture, such as a ruptured abdominal aortic aneurysm; and necrotizing fasciitis, which is a deep bacterial infection along the fascial plane, causing the patient to be critically ill, with severe pain and crepitus under the skin, and it’s a surgical emergency.

Alright, now that unstable patients are stabilized, let’s talk about the stable ones. Your first step here is to obtain a focused history and physical examination. You should find out what type of operation the patient had and when, and quickly assess for any signs of acute abdomen. Now, if you find a severely distended and rigid abdomen with diffuse tenderness, rebound pain, guarding, and sometimes tachycardia and tachypnea, the patient has an acute abdomen, which is a surgical emergency.

So, call the surgical team immediately for consultation and a possible exploratory laparotomy. Surgery should not be delayed to get additional diagnostic tests, as exploratory laparotomy is both therapeutic and diagnostic. It might reveal some important diagnosis like intra-abdominal bleeding, gross GI tract spillage, or abdominal sepsis. If there’s time though, you may still get some imaging, such as a bedside ultrasound to look for free fluid, or an upright chest x-ray to check for free air.

Alright, once you have ruled out acute abdomen, the next step is to assess for other causes of abdominal pain. Let’s first talk about superficial abdominal pain, which is limited to the skin and the abdominal wall. Most patients will describe this type of pain as localized soreness, and they can often point with one finger to the exact location of the pain. The most urgent cause of superficial abdominal pain is fascial dehiscence. Now, fascial dehiscence most commonly occurs in patients who underwent open abdominal or pelvic procedures. Risk factors for poor healing include obesity, diabetes, or immunocompromised status due to steroid use.

History usually reveals the sudden onset of pain and distention after feeling a “popping” sensation around the incision site. The “popping” sensation is caused by tearing of the approximated abdominal wall edges, which might occur when lifting heavy objects, usually within 4 weeks of surgery, since the edges haven’t properly healed yet. The physical exam might reveal a soft abdomen with a large incision and a possibly tender bulge that protrudes on Valsalva, which is actually a hernia. The next step is to get an ultrasound or CT. The imaging might show separation of the fascial layers, which confirms the diagnosis of fascial dehiscence. In some cases, dehiscence can lead to an urgent condition called evisceration which is when abdominal organs protrude through the open wound.

Another cause of superficial postoperative abdominal pain is formation of a seroma or hematoma, which are fluid collections composed of either serous fluid or blood. They usually occur near the incision site, because the vessels or tissues that were cut during surgery can leak between tissue planes created with surgical dissection. If there is bleeding into the rectus muscle, a rectus sheath hematoma can form.

Patients typically report mild pain, a normal diet, and unchanged bowel habits. However, if they report a rapidly enlarging mass around the surgical site, it should make you suspicious of seromas or hematomas. The physical exam might reveal a soft, non-distended abdomen with a palpable, possibly tender, well-circumscribed mass around the surgical site. If this is the case, order an ultrasound. If it shows a fluid-filled collection, the diagnosis of seroma or hematoma is confirmed.

Next, let’s talk about superficial surgical site infection, or SSI for short. Patients with SSIs usually report mild to moderate pain around the incision site, sometimes with a fever. On physical exam, you will see a soft, non-distended abdomen, with erythema, mild induration which is thickening or hardening of the skin, and tenderness around the incision. If you suspect SSI, mark the edges of the erythema to track its progression. If the erythema is spreading, and especially if you see purulent drainage, the diagnosis is SSI. On the other hand, if there’s minimal erythema ​​located just on the wound edge or around sutures and staples, with little to no drainage, the pain is likely from the normal wound healing process.

Alright, now that we’re done with the superficial abdominal pain, let’s switch gears and talk about deep abdominal pain. Deep abdominal pain is related to intra-abdominal organ space. It can present in different ways. Determining if it’s diffuse or localized, crampy or dull, or what helps make it better or worse can give clues about the underlying cause. Now, because this pain can indicate an organ pathology, it can be life-threatening.