Acute Abdominal Pain. Diagnostic Frameworks

Anatomy-Based Approach

I’m discussing an approach to acute abdominal pain diagnostic frameworks for acute abdominal pain, either based on anatomic region or by organ system. The former is more common. Using the region to organize the list of possible diagnoses, the abdomen can be divided into four quadrants, with the humble Lycos at the center. However, it’s probably even better to divide it into nine regions: right upper quadrant, epigastria, left upper quadrant, left flank, left lower quadrant, suprapubic (rarely called hypogastric), right lower quadrant, right flank, and parry umbilical in the center because this nine-region framework is the most common. Let’s take a closer look at it.

Region-Based Diagnostic Approach

When trying to consider what diseases might cause pain located in a certain region, the simplest principle is to consider what structures are within that region. So, pain in the right upper quadrant suggests liver or biliary pathology, while pain in the left upper quadrant could be from the spleen.

Epigastric Region

  • Now I’m going to go through specific ideologies while traveling around the abdomen. Starting in the epigastria region, pain located here can be from gastroesophageal reflux disease, gastritis, peptic ulcer disease, gastroparesis (most commonly a complication of diabetes), pancreatitis, and occasionally referred pain from acute coronary syndrome.

Left Upper Quadrant

  • Pain in the left upper quadrant can be from a splenic infarct, splenic abscess, or splenic rupture, a sub-diaphragmatic abscess, or referred pain from a left lower lobe pneumonia.

Flank Pain

  • Pain in either flank can be from nephritis, which is pyelonephritis (infection of the kidney), or a perinephric abscess (an abscess adjacent to the kidney).

Peri-Umbilical Pain

  • Perry umbilical pain is most commonly from simple viral gastroenteritis but could also be from a small bowel obstruction, mesenteric ischemia (which is like angina of the guts), or a ruptured abdominal aortic aneurysm.

Suprapubic Pain

  • Suprapubic pain can be from cystitis or a simple urinary tract infection.
  • It can also be caused by pelvic inflammatory disease (a severe complication of sexually transmitted infections seen in women).
  • Another potential cause of suprapubic pain is an ectopic pregnancy (which occurs when an embryo is implanted somewhere other than the uterus, resulting in a non-viable pregnancy and posing a life-threatening risk to the mother).

Pain in the Right and Left Lower Quadrants

  • Pain in the right and left lower quadrants shares similar pathologies.
  • Common causes include ovarian and testicular torsion, a ruptured ovarian cyst, a tubo-ovarian abscess, and ectopic pregnancy.

Differences Between Left and Right Lower Quadrants

  • Appendicitis pain is typically located in the right lower quadrant, except in cases with unusual anatomic variations in intra-abdominal organs.
  • Diverticulitis is more commonly found on the left side than on the right.

The Right Upper Quadrant: Complex Liver and Biliary Pathologies

  • The right upper quadrant stands out as a distinctive entity due to its complexity and the numerous potential liver and biliary pathologies that can occur in this region.

Causes of Right Upper Quadrant Pain

  • Right upper quadrant pain can be categorized into those arising from the liver, those related to the biliary system, and other causes of hepatic pain.

Infectious and Non-Infectious Etiologies

  • Causes of hepatic pain can further be classified into infectious and non-infectious factors.

Acute Abdominal PainCauses of Right Upper Quadrant Pain

  • Right upper quadrant pain can be categorized into those arising from the liver, those related to the biliary system, and other causes of hepatic pain.

Infectious and Non-Infectious Etiologies

  • Causes of hepatic pain can further be classified into infectious and non-infectious factors.

Infectious Causes of Hepatic Pain

  • Infectious causes include acute viral hepatitis and liver abscess.

Non-Infectious Causes of Hepatic Pain

  • Non-infectious causes encompass alcohol and medication-induced hepatitis, hepatic congestion from heart failure, and Budd-Chiari syndrome (caused by obstruction of the hepatic vein).

Biliary Pathologies

  • Biliary pathologies can also be divided into infectious and non-infectious categories.

Infectious Biliary Pathologies

  • Infectious biliary pathologies encompass acute cholecystitis (inflammation and infection of the gallbladder) and acute cholangitis (inflammation and infection of the common bile duct).

Non-Infectious Biliary Pathologies

  • Non-infectious pathologies of the gallbladder include simple gallstones (leading to biliary colic) and choledocholithiasis (a gallstone trapped within or actively passing through the common bile duct).

Other Causes of Right Upper Quadrant Pain

  • In addition to liver and biliary-related pathologies, right upper quadrant pain can also stem from other conditions, including referred pain from a right lower lobe pneumonia and a right-sided sub-diaphragmatic abscess.
Generalized or Poorly Localized Causes of Acute Abdominal Pain
  • Acute abdominal pain can sometimes present in a generalized or poorly localized manner. Conditions such as inflammatory bowel disease, infectious colitis (such as C. difficile), spontaneous bacterial peritonitis (occurring in patients with chronic ascites), secondary peritonitis (typically occurring from bowel perforation), and diabetic ketoacidosis are some examples of conditions that may result in non-specific abdominal pain.
Relatively Rare but Important Causes of Acute Abdominal Pain
  • While relatively rare, certain conditions can lead to acute abdominal pain and should not be overlooked. These include adrenal insufficiency, acute intermittent porphyria, abdominal migraine, angioedema (notably, angioedema can cause gut-related symptoms in addition to its more common swelling of mucous membranes in the face and throat), colonic pseudo-obstruction, herpes zoster (sometimes with abdominal pain preceding the unilateral vesicular rash by a few days), and a rectus sheath hematoma.

Patterns of Abdominal Pain Radiation”

Some ideologies of abdominal pain have common patterns of radiation. For example, pyelonephritis typically radiates around the flank to the lateral back, while nephrolithiasis radiates to the groin. Hepatic and biliary pathology often radiates to the right shoulder, and pain from pancreatitis and a triple A can radiate straight backward.

Understanding Appendicitis Pain Patterns and Abdominal Localization”

When it comes specifically to appendicitis, there is a classic migratory pattern to the pain. Early appendicitis, triggering just visceral pain fibers, is first felt not in the right lower quadrant but rather in the paraumbilical area, where its actual location is kind of vague and not yet associated with tenderness. In the next phase, as the peritoneum overlying the appendix becomes inflamed, the pain is now felt more in the right lower quadrants and is associated with significant tenderness. In the late phase, if the appendicitis is not identified and treated in a timely fashion, perforation occurs, leading to generalized pain along with peritoneal signs from secondary peritonitis. Visceral pain fibers are poorly localized compared to somatic fibers that innervate the peritoneum. As a consequence, despite the specific anatomic framework reviewed earlier, pain does not always map neatly to specific abdominal quadrants or regions. For example, visceral pain from foregut structures is most common in the epigastric region but can be found in either the right or left upper quadrants or near the umbilicus. Painful mid-gut structures can extend into the epigastrium and suprapubic regions. Hindgut structures can lead to pain throughout half the abdomen. Pain from the GU system and reproductive systems can be widespread, and even pain from the liver and biliary system can extend outside the right upper quadrants.

“Step-by-Step Evaluation of Abdominal Pain: Importance of History”

Now I’ll shift to discussing the step-by-step evaluation of abdominal pain, starting from the history. One of the most important questions is the chronology of the pain, for example, its acuity of onset. An extremely abrupt onset suggests a bowel perforation or vascular catastrophe, including intra-abdominal thromboembolism, ruptured triple-A, and ovarian or testicular torsion. How long has the pain been present for, and whether it is episodic or continuous? As a general rule, episodic pain suggests a less imminently dangerous pathology, such as biliary colic, peptic ulcer disease, GERD, chronic mesenteric ischemia, and gastroparesis. But that rule isn’t perfect since intermittent epigastric pain could be an atypical presentation of acute coronary syndrome.

Diagnostic Clues: Assessing Pain Location, Radiation, and Exacerbating Factors”

Location and radiation of pain is helpful at narrowing down diagnostic possibilities. Determine what the exacerbating factors are. For example, pain related in any way to food intake suggests either upper GI, pancreatic, or biliary pathology. Ask about the presence of associated symptoms, including nausea and vomiting, diarrhea or constipation, evidence of GI bleed, lack of flatus or passing gas, fever, jaundice, dysuria or hematuria.

“Comprehensive Patient Assessment: Gathering Essential Medical and Lifestyle Histories”

Take a past medical and surgical history, and a gynecological history, medication history, sexual history for STI risk factors, substance use history (particularly alcohol), travel history, and a general exposure history. These critical components of the patient’s history provide a holistic view that aids in the diagnostic process and ensures a thorough understanding of their health and potential risk factors.

Acute Abdominal Pain“Conducting a Targeted Physical Examination: Assessing Abdominal, Pelvic, and Cardiopulmonary Health”

After vitals, a focused physical exam should, of course, include a thorough abdominal exam. If any type of reproductive pathology is on the differential for a female patient, a pelvic exam should be performed. Since cardiac and pulmonary disease can refer to the upper abdomen, those exams should be performed as well. You may notice here that I have not listed a rectal exam; that’s because it’s generally not indicated unless anal, rectal, or prostatic disease is specifically suspected.

“Essential Laboratory Tests for Evaluating Acute Abdominal Pain”

Key labs in the workup of acute abdominal pain include CBC (Complete Blood Count), LFTs (Liver Function Tests), metabolic panel, and a lipase test. If the patient is a woman of childbearing age, get a urine hcg (human chorionic gonadotropin) to screen for pregnancy, even if she reports no sexual activity. Patients are sometimes not forthcoming, and an ectopic pregnancy is not a diagnosis you or your patient can afford to miss.

“Selecting Imaging and Diagnostic Tests for Acute Abdominal Pain”

If acute bowel ischemia is suspected, an elevated lactate would be consistent with infarction. Unless the patient is young, healthy, and without cardiovascular risk factors, order a troponin and an ECG to rule out acute coronary syndrome. If the pain is upper abdominal or where the patient has concurrent pulmonary symptoms, order a chest x-ray. If the patient reports either dysuria or hematuria, check a UA (urinalysis) plus or minus urine culture depending on suspicion for a urinary infection. There are numerous indications for either a CT (computed tomography), ultrasound, or rarely other imaging modalities. While, as a general rule, at least in the United States, clinicians over-rely on imaging in most circumstances, in my experience, acute abdominal pain is not one of them.

“Navigating Acute Abdominal Pain: An Alternate Approach to Diagnostic Algorithms”

n my approach to symptom, I usually present a diagnostic algorithm that one could follow to arrive at the single most likely diagnosis. But with acute abdominal pain, there are just too many ideologies to reasonably include in one algorithm. So, instead, I’m going to review a handful of illness scripts for some of the most common diagnoses, which will compare and contrast typical historical features, risk factors, common exam findings, and the relevant diagnostic tests. This approach offers a more comprehensive understanding of the diagnostic landscape when it comes to acute abdominal pain.

Breaking Down Acute Abdominal Pain: Causes and Contrasts”

I’ll divide these scripts in half, starting with causes of general and/or more midline pain, and will then separately compare and contrast the four most common causes of right upper quadrant pain. This segmented approach will provide a clear and focused understanding of the diverse spectrum of acute abdominal pain etiologies and enable us to delve deeper into each category for a more targeted evaluation.

First, let’s compare and contrast peptic ulcer disease (PUD), gastroenteritis, small bowel obstruction (SBO), appendicitis, and pancreatitis.

“Peptic Ulcer Disease (PUD): An Overview”

In PUD, the pain is epigastric, occasionally radiating to the back. It may be triggered by eating, and there is occasionally associated nausea and vomiting and/or overt signs of GI bleeding like melena, but these are usually absent. Risk factors include NSAID use and H. pylori infection. Physical exam can show mild to moderate epigastric tenderness. If there are peritoneal signs present, the ulcer has likely perforated and needs a surgeon. Routine blood tests are usually unremarkable unless the patient has significant bleeding. PUD is diagnosed via EGD (Esophagogastroduodenoscopy), which should be supplemented with testing for H. pylori.

“Understanding Gastroenteritis: Symptoms, Diagnosis, and Testing”

When it comes to gastroenteritis, pain is typically parry umbilical, often cramping, and associated with nausea, vomiting, and diarrhea. In most cases, there aren’t really significant risk factors outside of an outbreak. The exam will show mild to moderate Perry umbilical or generalized tenderness but no rigidity or peritoneal signs. Fever and signs of dehydration are common. The only typical abnormal blood test is an elevated white blood cell count. Diagnosis is a clinical one, not requiring any imaging or endoscopy. In just the last several years, some US medical centers have begun employing stool PCR panels for some patients presenting with diarrhea to identify the specific pathogen.

“Deciphering Small Bowel Obstruction (SBO): Symptoms and Diagnosis”

In a small bowel obstruction (SBO), the pain is typically periumbilical and crampy. It’s associated with nausea and vomiting, abdominal distension, and an absence of flatus. Risk factors for an SBO include prior abdominal or pelvic surgery, hernias, foreign body ingestion, inflammatory bowel disease, and an intestinal tumor. The exam usually shows abdominal distension. There may be high-pitched rushing bowel sounds. There may be signs of dehydration, and peritoneal signs suggest perforation or infarction. Even though an SBO can usually be diagnosed on history and exam alone, these patients should all get a CT to identify the location of the obstruction and to search for potential causes. If, for some reason, CT is not available, plain films are a reasonable alternative to definitively confirm the diagnosis. In which case, upright and supine abdominal films should be ordered, plus or minus an upright chest x-ray, which can better identify the presence of free air.

Acute Abdominal Pain“Decoding Appendicitis: Symptoms, Signs, and Diagnosis”

Pain from appendicitis is classically present in the right lower quadrant but often begins in the paraumbilical region. Nausea, vomiting, and anorexia usually follow the onset of pain rather than the other way around. If there is severe generalized pain, perforation is likely. There are no major risk factors for appendicitis. On exam, the most notable finding is tenderness in a specific location called McBurney’s point, which is located one-third of the distance along an imaginary line from the anterior superior iliac spine to the umbilicus. There are some other classic but less discussed findings, such as Roving’s sign, obturator sign, and psoas sign. Patients are often febrile, and once again, peritoneal signs suggest perforation. Significant labs in appendicitis include high white counts and an elevated CRP. While an elevated CRP would be expected in some other abdominal diseases, such as peritonitis and acute cholecystitis, for some reason, it’s more discussed as a feature of appendicitis specifically. There’s also a clinical prediction rule called the Alvarado score, which assigns points to various historical, exam, and lab features to give an overall probability of the diagnosis. Any patient with suspected appendicitis should undergo imaging, which can be either CT or ultrasound. The choice of which is institution, clinician, and situation-dependent.

“Cracking the Code of Pancreatitis: Symptoms, Causes, and Diagnosis”

In pancreatitis, patients present with epigastric pain radiating to the back that’s exacerbated by eating and relieved by sitting up and leaning forward. It’s usually associated with nausea and vomiting. This symptom is more commonly associated with pancreatitis than with the other diagnoses in this chart. Risk factors or ideologies for pancreatitis include alcohol and gallstones, which together account for the majority of cases. Less common causes include ERCP, hypertriglyceridemia, and a variety of medications. On exam, severe cases can present with shock and paraumbilical or flank ecchymosis, which suggests hemorrhage secondary to pancreatic necrosis, a particularly worrisome sign. The most notable abnormal lab is an extremely elevated lipase, typically more than three times the upper limit of normal. While a CT scan is not considered necessary for the diagnosis, it can assess for complications and help identify gallstones in the pancreatic duct as a potential causative factor.

Biliary Colic: Unveiling the Symptoms, Risk Factors, and Diagnosis”

In biliary colic, caused by gallstones within the gallbladder, the pain is typically episodic, lasting 30 minutes to several hours. It’s often triggered by eating, and there is no associated jaundice. Risk factors include female sex, pregnancy, obesity, rapid weight loss, and diabetes. On exam, patients are usually afebrile, and the physical exam is usually unremarkable as are routine blood tests. A right upper quadrant ultrasound will show gallstones and help clinch the diagnosis. But this is a non-emergent study. If the clinical presentation is classic, the patient can follow up with a surgeon.

“Acute Cholecystitis: Unraveling Symptoms, Risk Factors, and Diagnosis”

In acute cholecystitis, the pain is progressive over hours. Nausea and vomiting are common, and since the common bile duct is not involved, there is no jaundice. The most notable risk factor for acute cholecystitis is the known presence of pre-existing gallstones. On exam, patients are often febrile. The classic finding is an increase in right upper quadrant tenderness on inspiration when the diaphragm descends, pushing the liver and gallbladder into the examiner’s stationary hands. This is known as Murphy’s sign. There’s also something called the sonographic Murphy sign in which pain is worse with inspiration when pressure is applied to the right upper quadrant with an ultrasound probe at the exact location of the gallbladder since the examiner can directly see it on the screen. This is thought to be more specific than the classic Murphy sign. Routine lab tests usually reveal an elevated white count with normal or near-normal LFTs. A definitive diagnosis can usually be made with a right upper quadrant ultrasound.

“Acute Cholangitis: Recognizing Symptoms, Risk Factors, and Diagnostic Steps”

In acute cholangitis, the pain is similar to acute cholecystitis, and nausea and vomiting are also common. However, jaundice also occurs. Risk factors for acute cholangitis include benign biliary strictures and malignant obstruction of the biliary system, including pancreatic tumors. As a very general rule, patients appear more ill than in other common causes of right upper quadrant pain, but this is less often the case in the elderly and in those on immunosuppressive medications. Common test findings include a high white count, high bilirubin, which is predominantly direct or conjugated bilirubin, high alkaline phosphatase, and there may or may not be a mild to moderate elevation of AST and ALT. If, after the history, exam, and blood tests, the pretest probability of cholangitis is high, one can proceed directly to an ERCP. Otherwise, consider a right upper quadrant ultrasound.

“Deciphering Acute Hepatitis: Symptoms, Causes, and Diagnostic Steps”

The last diagnosis to discuss is acute hepatitis, which is acute infection and/or inflammation of the liver. The symptoms of acute hepatitis can be similar to those of acute cholangitis, though in my experience, the onset is slightly more prolonged. Risk factors, or more appropriately, ideologies here, include hepatitis viruses, particularly A, alcohol, acetaminophen toxicity, and autoimmune hepatitis. There are many other causes of acute hepatitis, but these four cover the overwhelming majority in the US and other Western countries. On exam, fever is sometimes present, and there can be a variety of findings related to liver dysfunction depending on the severity and acuity of presentation. Labs include a high white count, extremely elevated AST and ALT, often over 1000, high bilirubin, classically with direct and indirect being roughly equal, and an elevated INR. Other tests you should order include hepatitis virus serologies and an acetaminophen level, though a single number is impossible to interpret in the absence of a known time of acute drug ingestion. Also, if another etiology of the hepatitis has not been clearly established, autoantibodies for autoimmune hepatitis are reasonable to order.

When discussing acute abdominal pain, it’s common to hear the term “surgical abdomen.” Use of this term implies that the underlying etiology requires an emergent evaluation by a surgeon. Specific exam characteristics that are consistent with a surgical abdomen include rigidity, also known as involuntary guarding, which is the most concerning of abdominal physical findings. Unusually severe tenderness to palpation, signs of peritonitis, known as peritoneal signs, include rebound tenderness. This is the finding that pain caused by slow abdominal pressure applied by the examiner’s hands is not as severe as pain caused by the quick release of that pressure. It includes a positive cough test, in which pain is worsened by coughing, the bed bump test, in which it is worsened by the examiner bumping the bed hard, which works best on a gurney rather than a sturdy hospital bed, or the heel strike test, in which pain is worsened by the examiner firmly striking the patient’s heel. In ambulatory patients, the heel strike test can be done by asking the patient to stand and jump in place. Absent bowel sounds. None of these findings in isolation necessarily indicate a surgical abdomen, but seeing multiple of them in a patient whose history is consistent with a possible surgical emergency would suggest this general situation. Also, not every surgical emergency presents with a surgical abdomen, specifically emergencies which are extra-peritoneal, such as a ruptured aortic aneurysm.

The term “surgical abdomen” is sometimes used interchangeably with the term “acute abdomen,” although some clinicians use the latter term more broadly to mean any patient with acute abdominal pain and any notable physical exam findings irrespective of likely pathology.

Finally, I’ll end by listing those conditions to particularly consider in patients with abdominal pain who are presenting with shock at the time of initial presentation. These include acute cholangitis, bowel perforation, bowel infarction, ruptured ectopic pregnancy, ruptured AAA, splenic rupture, any condition with concurrent massive GI bleed, and an acute myocardial infarction.


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