Approach to pneumoperitoneum and peritonitis (perforated viscus): Clinical sciences

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Introduction0:00–0:50

Pneumoperitoneum, or the presence of air or gas within the peritoneal cavity, is considered a surgical emergency because it often indicates perforation of the gastrointestinal tract.
On the other hand, peritonitis refers to the inflammation of the peritoneum. Depending on the etiology, peritonitis can be divided into primary, secondary, and tertiary.
Here is a clinical pearl! Even a small amount of bacterial seeding within the peritoneal space can progress quickly and become life-threatening.
Keep in mind that bacterial infections can be spontaneous if there are preexisting ascites from liver or kidney failure or come from the GI tract through transmural infection or perforation.

Acute management0:50–1:17

When approaching a patient with signs and symptoms suggestive of peritonitis and pneumoperitoneum, first perform an ABCDE assessment to determine if the patient is unstable or stable.
If the patient is unstable, stabilize their airway, breathing, and circulation by providing supplemental oxygen, obtaining IV access, and continuously monitoring their hemodynamics.

History and physical1:17–2:03

Alright, now that unstable patients are taken care of, let’s talk about stable ones. Your first step here is to obtain a focused history and physical examination and assess for an acute abdomen.
Patients with acute abdomen usually report severe abdominal pain, nausea, vomiting, and bowel changes, as well as fever, chills, and generalized malaise.
On a physical exam, you’ll find abdominal distension, tenderness, rigidity, rebound, guarding, decreased/absent bowel sounds.
Now, when your clinical exam indicates an acute abdomen, the first thing you want to do is to find and treat the underlying cause.
Let's first look at pneupoeritoneum. When your clinical exam indicates an acute abdomen, your next step is to assess for pneumoperitoneum by obtaining an upright chest or 3 view abdominal x-ray.

Pneumoperitoneum2:03–2:43

When it comes to the x-ray, air under the diaphragm is pathognomonic of pneumoperitoneum. Because pneumoperitoneum of any source is a surgical emergency, you need to use specific elements of the patient’s history to guide your differential diagnosis instead of ordering additional tests which can delay operative management.Alright, if the patient reports the acute onset of severe postprandial epigastric pain, is unable to lie in a supine position, and has a history of GERD you should consider a perforated peptic ulcer.

Perforated PUD, appendicitis, and diverticulitis2:43–3:51

Call the surgical team for emergent operative intervention. The definitive diagnosis will be made intraoperatively.Another cause of pneumoperitoneum is perforated appendicitis.
History might reveal a young otherwise healthy patient with several days of worsening periumbilical or right lower quadrant pain.
Call the surgical team for emergent operative intervention. Again, the diagnosis of perforated appendicitis will be confirmed intraoperatively.Now, if a middle-aged or older patient with a history of diverticulosis and chronic constipation reports left lower quadrant pain, you should consider perforated diverticulitis.
This patient will need an emergent operation, which will confirm the diagnosis. On the other hand, if a patient above the age of 60 with a history of smoking reports anorexia, unintended weight loss, fatigue, as well as a personal or family history of cancer, you need to consider gastrointestinal malignancy like colon cancer as the cause of the perforation.

Perforated bowel secondary to neoplasm3:51–4:27

These patients need to be taken to the operating room right away for resection of the mass and diversion of the bowel such as colostomy or ileostomy.
A tissue sample of the mass should be sent for pathologic confirmation of the diagnosis.Finally, in an elderly patient with a history of previous abdominopelvic operation who presents with bilious vomiting, PO intolerance, and bowel changes like constipation, obstipation, or overflow diarrhea, you need to consider small bowel perforation secondary to small bowel obstruction.

Small bowel perforation secondary to SBO4:27–5:03

This happens when the obstruction causes proximal dilatation so much that the bowel wall becomes ischemic. Operative management in this case is to identify the obstruction and resect the ischemic or necrotic segment.

Peritonitis5:03–6:21

Now, let's move on to peritonitis. On an upright x-ray, you will have ruled out pneumoperitoneum, and start to consider peritonitis.
First, obtain a detailed history and physical to determine differential diagnoses of peritonitis. Many signs and symptoms of peritonitis can overlap with pneumoperitoneum such as diffuse abdominal pain, nausea, vomiting, fever, chills, and bowel changes, as well as abdominal distension, rigidity, diffuse tenderness, rebound, and guarding on physical exam.
Keep in mind that peritonitis is a clinical diagnosis in the absence of radiologic evidence of pneumoperitoneum. Your next step is to obtain a full set of labs including CBC, CMP, that includes liver function tests; as well as lactate, lipase, and amylase.
Labs will generally show leukocytosis with a left shift and metabolic acidosis, while elevated LFTs, lactate, lipase, or amylase can help point to the underlying cause.
Next, obtain an abdominal and pelvic CT to narrow down the type of peritonitis.Let’s begin with primary peritonitis. On CT, you can expect to see free fluid in the abdomen with a normal GI tract.

Primary peritonitis6:21–7:24

Here, the CT scan is not used to diagnose peritonitis but to rule out the GI tract as the source of the peritoneal infection and inflammation.
If you suspect primary peritonitis, the next step is to perform a paracentesis and send the peritoneal fluid for analysis, which should include cell count, albumin, protein, glucose, LDH, and cultures.
With the results, you need to calculate the serum-ascites albumin gradient. A SAAG of less than 1.1 indicates a direct peritoneal cause of peritonitis, while SAAG greater than or equal to 1.1 suggest complications of portal hypertension like spontaneous bacterial peritonitis.An obvious cause of primary peritonitis with a SAAG below 1.1 is peritoneal dialysis or PD catheter dysfunction or infection.

PD catheter dysfunction7:24–8:14

The SAAG is low in these patients because renal failure is often associated with low serum albumin. On history, patients typically report issues with their dialysis sessions such as feeling increased resistance in the inflow of dialysis fluid or decreased fluid output.
CT in these cases may show kinking or displacement of the catheter to support your diagnosis. Additionally, if you see cloudy peritoneal fluid with an elevated WBC count and polymicrobial growth on culture, you can make your diagnosis of PD catheter infection.

Peritoneal carcinomatosis8:14–8:59

Another differential diagnosis is peritoneal carcinomatosis. On history, patients typically report anorexia, unintended weight loss, and fatigue as well as a personal or family history of cancer.
The initial CT scan may show a primary malignancy or peritoneal seeding. Additionally, you might see elevated WBC with lymphocytic dominance on peritoneal fluid analysis, in which case the fluid needs to be sent for cytology in order to assess for specific cell types.
You can expect to find malignant cells on cytology, which will support your diagnosis of peritoneal carcinomatosis. Finally, peritoneal endometriosis is a rare and severe form of endometriosis where extrauterine endometrial cells are seeded within the peritoneal lining.

Peritoneal endometriosis8:59–10:21

Often, biologically female patients within childbearing age report abdominal distension and pain associated with their menstrual cycle.
On the initial CT scan, you might be able to see small endometriosis seeds or masses within the peritoneum or abdominal soft tissues but to make a definitive diagnosis, you need a tissue sample from a diagnostic laparoscopy with biopsy.
If you find any endometrial tissue here, the diagnosis of peritoneal endometriosis is confirmed. On the other hand, if you have a patient with a SAAG score of 1.1 or greater in the setting of underlying liver failure, you should suspect spontaneous bacterial peritonitis or SBP.
The peritoneal fluid analysis will show elevated WBC with polymorphic neutrophil predominance, and a high protein and a low glucose level.
Peritoneal fluid culture will be positive for single pathogen infection which confirms your diagnosis of SBP.Let’s move on to secondary and tertiary peritonitis.

Secondary and tertiary peritonitis10:21–11:32

Peritonitis is defined as inflammation and infection of the peritoneum from the GI tract. Bacterial seeding can occur if there’s a tiny perforation of the GI tract or sometimes through a transmural infection of the bowel wall in inflammatory bowel disease.
CT scan will show intraabdominal free fluid with inflammatory changes along the GI tract like bowel wall thickening or discontinuity, and signs of infection like a phlegmon or an abscess.
If you see these findings, you can diagnose secondary peritonitis.Lastly, tertiary peritonitis occurs as a part of the postoperative inflammatory process after an abdominopelvic operation.
Preexisting preoperative inflammatory processes like an intraabdominal infection or trauma can increase the risk of tertiary peritonitis.
If CT shows postoperative inflammatory changes with no new signs of infection, you can diagnose tertiary peritonitis, which is usually expectant and self-limiting.Alright, as a quick recap… While an upright abdominal or chest x-ray showing free air under the diaphragm is enough to diagnose pneumoperitoneum, history, and physical exam are needed to find the site of perforation like PUD, appendicitis, diverticulitis, large, or small bowel.

Review11:32–12:38

These patients require emergent operative management, which is therapeutic and diagnostic. On the other hand, peritonitis is classified as primary, secondary, and tertiary.
Primary peritonitis includes PD catheter dysfunction or infection, peritoneal carcinomatosis, endometriosis, or SBP. Secondary peritonitis arises from the GI tract via a transmural infection or perforation.
Lastly, tertiary peritonitis occurs as a part of the expectant postoperative inflammatory process after an abdominopelvic surgery.