Hello. Welcome back. Today, in this module of acute abdomen, we’re going to discuss some general principles.

Let’s start with a clinical scenario. Imagine yourself in the emergency department. You’re seeing

a 35-year old man who presents to the emergency department with three days of crampy

abdominal pain and diarrhea. He reports subjective fevers. On your physical examination,

he is tender to palpation in all quadrants of abdomen but he doesn’t demonstrate any rebound or guarding.

Think about this for just a second. Does this patient have a surgical abdomen? What is an acute abdomen?

These are some of the questions I hope to answer in this module. Acute abdomen is defined

as the sudden onset of abdominal pain regardless of the cause. The different layers of the peritoneum

are probably very familiar to you. Take a look at this image. The blue outline suggests the layers

of the peritoneum. The peritoneum has two layers, the parietal and the visceral. Abdominal pain

and the abdomen has classically been divided into nine quadrants. I’m going to differentiate

a little bit between the pain of visceral and parietal peritoneum. First, the visceral peritoneum.

Pain is difficult to localize if the inflammation involves visceral peritoneum. This visceral pain

is often mediated by distension, ischemia, and felt largely in the midline of the abdomen,

although this can vary. But the parietal peritoneum, the nerve fibers go to one side or the other

of the spinal cord. This allows you to be easier to localize where the abdominal pain is.

Here, you see a wide variety of differential diagnosis based on the location of the abdomen.

Let’s go through them quickly. In the right quadrant of the abdomen, one has to consider

acute cholecystitis, cholangitis, and even hepatitis. In the right lower quadrant of the abdomen,

one considers appendicitis. In women, very importantly consider GYN pathology including

ovarian torsion/cysts or pelvic inflammatory disease. Let’s move over to the left side of the abdomen.

In the left upper quadrant, one has to consider peptic ulcer disease. Midepigastric pain is typically

associated with pancreatitis. Again, in the left upper quadrant of the abdomen, the spleen

or kidney stones can cause pain. How about the left lower quadrant of the abdomen?

We think about diverticulitis, colonic volvulus, colon perforation. Perhaps the most difficult

to diagnose are midline structures such as the small intestines classically associated with small bowel

obstruction or in this situation, a small bowel perforation. So, what as a surgeon, what is my approach

to the patient? When I see that clinical scenario of the healthy 38-year old, well, I ask myself

three very important questions. First, does the patient need surgery? Next, how soon does the patient

need surgery? Lastly, is there any additional workup necessary? You will find throughout the lectures

for surgery that we’re commonly thinking about these three questions. This is why one of the reasons

we want you to consult a surgeon as early as possible during your workup of the acute abdomen.

Let’s take a look at some of the common scenarios that may require surgery and also known as

a surgical abdomen. Remember, these are high-yield topics for the USMLE examination. First perforation;

if you get an abdominal X-ray and there is free air under the diaphragm as demonstrated in this image,

this patient needs an urgent exploratory laparotomy without further workup. Unfortunately,

the presence of the free air or pneumoperitoneum doesn’t necessarily tell you what the pathology is.

Next, let’s talk about ischemia. Bowel ischemia is less likely than perforation, nevertheless,

a very important cause of acute and surgical abdomens. Classically described as thumbprinting

and pneumatosis, pneumatosis occurs because the intestinal lining mucosa is the first and most susceptible

lining to ischemia. As the mucosa breaks down, air is then allowed to track transmurally into the lining

of the small intestines resulting in pneumatosis. You will see this on an abdominal X-ray

as thumbprinting and pneumatosis. Next, let’s talk about bleeding. Although the vast majority

of GI bleeding is treated nonoperatively and we have great success in doing so nonoperatively,

when the patient becomes hemodynamically unstable such as low blood pressure or hypotension,

peritoneal signs or they have required a significant amount of blood transfusion, that might be

an indication for emergency surgery. Lastly, small bowel obstruction; small bowel obstruction

is one of the most common diagnoses in the United States, one of the most common surgical diagnoses

in the United States. Luckily for most of these patients, they don’t require surgery. Bowel obstruction

which will be discussed in a later lecture module is usually associated with previous surgeries.

Here in the abdominal X-ray particularly in an upright abdominal X-ray, you’ll notice air fluid levels.

Clinical pearls: remember, not all acute abdomens require surgery, although all surgical abdomens

are most likely acute abdomens. Another high yield fact for your examination, signs of peritonitis,

whether it’s rebound or guarding requires surgical exploration without further workup.

Thank you for joining me for this lecture on acute abdomen.