An Approach to the Acute Abdomen
Doctor, I have excruciating abdominal pain ! An Approach to the Acute Abdomen
Introduction
Clinical Examination
Differential Diagnosis
Evaluation Priorities
Context: casualty
Introduction
Severe abdominal pain is a common reason for a visit to the emergency department. A number of cases settle spontaneously, yet others may harbour lethal conditions that require you to make a rapid, accurate diagnosis and urgent intervention.
The patient groaning with abdominal pain, lying on a hospital stretcher is the true test of surgical diagnostic thinking- it easily differentiates the competent clinician with a clear, structured approach, from a befuddled, uncertain one. It takes the consultant one post-call ward round to decide which registrars to trust, and which ones need to go back to the basics !
There is no substitute for a sound approach and thorough clinical evaluation of such cases. You have to take time, ask a comprehensive set of questions about the presenting symptoms, associated complaints, and a systematic enquiry.
Always examine the patient properly. Do not throw your hands up in the air, and “just do bloods and order a CT”; apply your mind and MAKE A CLINICAL DIAGNOSIS! Don't poke the patient’s belly through his/her clothes and run off to “look at the scans”. Be inquisitive, and take pride in the clinical assessment of each case.
Try to decide if this is a brand new symptom, or if it reflects a progression of long-standing disease. Is this an acute problem or an exacerbation of a chronic condition?
DESCRIBE THE PAIN THOROUGHLY: define the presenting complaint
Location and radiation | Where is it, and where does it radiate to? RUQ- liver or biliary tree Back- pancreatitis Groin-renal colic RIF- appendicitis |
Temporal elements | The onset, frequency, and duration of the pain are helpful features Pancreatitis= gradual and persistent Perforation/ peritonitis = sudden onset & high intensity |
Quality | Burning pain= gastritis /peptic ulcer disease Colicky/cramping pain=gastroenteritis / intestinal obstruction. |
Severity | The severity of the pain generally is related to the severity of the disorder, especially if acute in onset Excruciating= acute mesenteric ischemia high intensity= biliary / renal colic / small bowel obstruction moderate= gastroenteritis, appendicitis |
Precipitants or ameliorating factors | Identify what precipitates or improves the pain chronic mesenteric ischemia = starts within one hour of eating duodenal ulcers = relieved by eating and recur several hours after a meal pancreatitis = relieved by sitting up and leaning forward & strong association with alcohol intoxication Peritonitis = patients lie motionless on their backs |
ASK ABOUT ASSOCIATED SYMPTOMS: what else is going on?
GIT symptoms | Is the gut working or not?? nausea, vomiting, diarrhoea, dysentery, constipation, hematochezia, melena, and changes in the stool. When last did the patient pass flatus? Is the liver working or not? ask about jaundice and changes in the colour of urine and stool |
Genitourinary symptoms | Is there a genitourinary cause for their abdominal pain? This is quite common! dysuria, frequency, hematuria and retention |
Gynaecological history | Consider sexually transmitted diseases, pelvic inflammatory disease, and pregnancy in premenopausal women menstrual history (LMP, previous period, cycle length) use of contraception vaginal discharge or abnormal PV bleeding dyspareunia or dysmenorrhea |
Constitutional symptoms | fevers, rigors= peritonitis, UTI, cholangitis fatigue, weight loss, and anorexia =malignancy, TB, systemic illnesses, inflammatory bowel disease |
TAKE A COMPREHENSIVE HISTORY: this allows you to consider other causes, and contextualise the patient’s fitness for intervention
Cardio-respiratory symptoms | Could there be a non abdominal cause of pain? Does the patient have co-morbidities? cough, shortness of breath, orthopnea, exertional dyspnea, angina = pulmonary or cardiac aetiology for the pain? |
Past medical history | Previous abdominal surgery = ? bowel obstruction cardiovascular disease (CVD) = ?MI or mesenteric ischaemia recent trauma= ? traumatic pancreatitis HIV+ve= abdominal tuberculosis Previous malignancy= cancer recurrence/ obstruction? |
Medication history | Describe a comprehensive medication list, including over the counter medications NSAIDs= gastritis, peptic ulcer disease recent antibiotics= Clostridium difficile steroids = adrenal insufficiency recent chemotherapy = immunosuppressed & atypical presentations of abdominal pain. |
Precipitants & other aetiological factors | alcohol = pancreatitis, acute gastritis, hepatitis IV drug users= endocarditis, mesenteric ischaemia, hepatitis, drug withdrawal states Travel history= hepatitis, gastroenteritis, colitis, parasitic disease Recent blunt or penetrating trauma= delayed bowel perforation, pancreatitis, diaphragmatic herniae, liver haematoma, ruptured bladder |
Clinical Examination
Does the patient need active resuscitation? | Consider the following conditions: Any cause of peritonitis and septic shock Ruptured AAA Myocardial infarct mesenteric ischaemia & small bowel infarction Severe acute pancreatitis |
General examination | Pyrexia= peritonitis, TB, UTI, PID Anaemia= malignancy , chronic disorders, AAA (acute GIT bleeds seldom complain of pain) Jaundice= biliary obstruction, hepatitis, sepsis Dehydration/ malnutrition= bowel obstruction, malignancy, TB Peripheral adenopathy= malignancy |
Abdominal examination | Does the patient have clinical signs of peritonism or not? This takes much clinical experience and guidance. If unsure, take time and re-examine after an interval. Distract the patient whilst performing the examination Inspect- for scars, herniae, masses, distention (examine the groins & scrotum) Percuss- pain with gentle percussion= peritonitis Tympany = distended bowel dullness = mass/ organomegaly Shifting dullness = ascites Palpation- Distract the patient and be gentle! Start AWAY from the site of most pain, until the end of the examination. Muscular rigidity/"guarding" is an important early sign. Guarding is typically absent with deeper sources of pain such as renal colic and pancreatitis. Rebound tenderness = peritonitis Auscultation- active, high-pitched bowel sounds = early bowel obstruction. Absent bowel sounds= ileus Bruit or murmur= AAA, renal artery aneurysm |
Rectal and pelvic examination | patients with severe abdominal pain must have a rectal examination. Stool bolus= Fecal impaction & obstruction in older adults tender PR =retrocecal appendicitis & pelvic abscess blood PR= colitis, colorectal malignancy, bleeding PUD All women with acute lower abdominal pain should have a pelvic examination Cervical excitation tenderness= PID (Can also occur with peritonitis) Blood PV= miscarriage or failed abortion PV discharge= PID Tender PV, low BP & anaemia= ectopic pregnancy |
Differential Diagnosis
There are multiple diagnoses to consider, and unless you use a structured approach the clinical scenarios can feel overwhelming.
It is practical to consider a diagnostic algorithm that starts with a broad range of conditions and narrows down to the ones most pertinent to a surgical unit.
Whilst not very “scientific”, approach the aetiology of the abdominal pain by considering two categories, medical causes & surgical causes- if you are confident that the medical causes are not a factor, then the patient and the diagnosis is 100% your responsibility!
“Medical” causes of severe abdominal pain
Very common | Occasional | Rare |
Gastro-enteritis Pyelonephritis, renal colic, cystitis, Urinary retention PID | Colitis Pneumonia, Pleurisy MI, acute pericarditis DKA Acute hepatitis | Herpes zoster Porphyria Hypercalcaemic crisis Addisonian crisis Sickle cell crisis Lead poisoning Tabes dorsalis Phaeochromocytoma & hypertensive crisis |
“Surgical” causes of severe abdominal pain
To differentiate the surgical causes of an acute abdomen, decide on where the “epicentre” of the pain is, consider the anatomical structures in that region- accept that there may be overlap between diagnoses and that clinical symptoms and signs evolve over time.
Irrespective of the abdominal site of the pain, ALWAYS CONSIDER APPENDICITIS in the differential diagnosis. It is the commonest cause of peritonitis in any age group, and if misdiagnosed can be fatal.
Right upper quadrant pain | |
Common Causes | Clinical Features |
Biliary colic | Intense, dull discomfort located in the RUQ or epigastrium. Associated with nausea, vomiting, and diaphoresis. Generally lasts at least 30 minutes, plateauing within one hour. Benign abdominal examination |
| Cholecystitis | Prolonged (>4 to 6 hours) RUQ or epigastric pain, fever. Patients will have abdominal guarding and Murphy's sign |
| Cholangitis | Fever, jaundice, RUQ pain. |
| Liver abscess | Fever, RUQ pain, cachexia, anaemia |
| Appendicitis | Subhepatic location of the appendix can mimic biliary disease |
Rare causes | Budd-Chiari syndrome/ adrenal haemorrhage/ Fitz Hugh Curtis syndrome/metastatic liver disease/ complicated hydatid disease |
Left upper quadrant pain This is the least common location for severe abdominal pain; the aetiology overlaps significantly with the common causes of severe pain in the epigastrium | |
Rare causes | Clinical Features |
Splenic infarct | Associated with a variety of underlying conditions (e.g., hypercoagulable state, atrial fibrillation, and splenomegaly). Commonly presents with pain radiating to the tip of the shoulder, and sympathetic pleural effusion |
Splenic abscess | Associated with fever and LUQ tenderness may be a complication of splenic infarction |
Splenic artery aneurysm | LUQ pain, low Hb, and hypovolaemic shock – abdominal apoplexy. Most common in pregnancy |
Epigastric & central abdominal pain | |
Common Causes | Clinical Features |
Perforated PUD | Sudden, excruciating epigastric pain. Patient unable to move with typical board-like rigidity and peritonism |
Acute pancreatitis | Acute-onset, persistent upper abdominal pain radiating to the back. |
Gastritis | Abdominal pain, heartburn, nausea, vomiting, and hematemesis. True peritonism uncommon. Common following an ethanol binge. |
Liver abscess | Fever, RUQ pain, cachexia, anaemia. If the abscess is in left lobe of the liver it can cause excruciating epigastric tenderness. A mass may also be palpable |
Small bowel obstruction | Central, cramping, severe abdominal pain, with profuse biliary vomiting. Prominent abdominal distention. Peritonism only if the bowel is ischaemic |
Appendicitis | In the early phases of appendicitis, the pain is centrally located. In cases with a free perforation and generalized peritonitis, the pain is diffuse. |
Rare causes | Mesenteric ischaemia/ AAA/ acute on chronic pancreatitits/ pancreatic malignancy/ perforated gastric carcinoma/ primary peritonitis |
Lower abdominal pain | |
Common Causes | Clinical Features |
Appendicitis | Periumbilical pain initially that radiates to the right lower quadrant. Associated with anorexia, nausea, and vomiting. Low-grade pyrexia and localised peritonism |
Diverticulitis | Older patient. Pain usually constant in the left iliac fossa, and present for several days prior to presentation. May have associated nausea and vomiting. Local signs depend on the severity of local complications |
PID | Severe central or lateral pain. Sexually active. Vaginal discharge. Marked cervical excitation tenderness. Less impressive GI symptoms |
Rare causes | Crohn's disease, TB enteritis, acute colitis, Meckel’s diverticulitis, perforated colon carcinoma, torted ovarian neoplasm, endometriosis, iliopsoas abscess, intussusception |
Flags for uncommon diagnoses
Patients with concomitant diagnoses (co-morbidity) are still more likely to have a COMMON cause of abdominal pain, than a rare one, but the conditions below should alert you to some unusual pathology - just think about them!
HIV + | TB peritonitis, lymphoma, Kaposi sarcoma of the small bowel, CMV colitis, TB iliopsoas abscess |
Anaemia & Cachexia | Obstructed/ perforated GIT cancer, Crohn’s disease, TB |
Vasculopathy | MI, Bowel ischaemia, AAA |
Connective tissue disorders | Bowel ischaemia, serositis |
Renal failure | Primary peritonitis (in patients with peritoneal dialysis NB, or nephrotic syndrome) |
Liver failure | Primary peritonitis |
Elderly | Obstructed/ perforated GI cancer MI, Bowel ischaemia, AAA |
Infant | Necrotizing enterocolits, intussusception, Henoch Schonlein purpura |
Pregnant | Ectopic or extrauterine pregnancy, ovarian torsion, fibroid degeneration Abruptio placenta |
Recent chemotherapy | Colitis |
Psychiatry | Swallowed foreign body, trauma, fictitious disorder Urinary retention in Alzheimer's |
Evaluation Priorities
How sick is the patient?
Do I need to start a resuscitation protocol?
- Hb, blood gas, WBC
- Start IV fluid rehydration, consider early IV antibiotics
The acidotic or confused patient is critically ill and needs urgent intervention. Beware the young fit patient with a normal PH but a low PCO2(compensated metabolic acidosis) they may look well but decompensate quickly.
How bad is the pain?
Give adequate analgesia, typically parenteral opiates
What is the diagnosis?
Have I excluded “medical causes” of acute abdomen?
Check urine, pregnancy test, CXR, AXR, ECG, U&E, LFT, lipase
Does the patient OBVIOUSLY need an urgent operation?
Don't delay surgery when it is needed! Get on with it!
I am not quite sure what is going on, and I need more information
Re-evaluate the patient clinically at 6-12 hour intervals, review with a colleague
Commonly used emergency investigations
Test | Ideal context | Issues to consider |
Abdominal US | Thin patient, good in biliary and gynae pathology | Operator dependent, but widely available and relatively cheap |
Abdominal CT | Best for obese patients, or suspected retroperitoneal or pancreatic pathology | By far the best investigation but it is expensive, uses IV contrast, and is not always available |
Laparoscopy | Excellent to differentiate appendicitis from PID | Commits patient to surgery uses theatre resources, requires surgical expertise |
- A number of acute surgical conditions evolve (or resolve!) over 12 to 24 hours, and some diagnostic mysteries become obvious with time and re-evaluation.
- You will develop clinical wisdom to accept uncertainty, and constantly re-evaluate your diagnosis in light of the clinical state of the patient.
- Don't be dogmatic. If the patient isn’t responding to your management, revisit the story and the working diagnosis. Think again.
- Don’t accept “diagnostic labels” until they are unequivocally proven.
What other investigations must I consider?
Be selective in the investigations, and use common sense instead.
The investigations below are occasionally helpful.
Test | Ideal context | Issues to consider |
Contrast study | Can demonstrate obstructions or subtle leaks from the GIT, especially from the oesophagus | Largely replaced by CT scans with either oral or rectal contrast. |
Endoscopy | Seldom helpful in acute abdominal pain | VERY uncomfortable for the patient |
Angiography | Vascular cases with occult bleeding or false aneurysm | Requires very specific endovascular skills |
ERCP | In selected cases of cholangitis only | Requires very specific endoscopic skills |
SHOULD I OPERATE OR NOT?
The decision to intervene surgically is the most significant of all the issues that pertain to the management of a patient with acute abdominal pain.
Some cases HAVE to undergo emergency surgery, whilst others will be harmed by unnecessary surgery. Correct case selection is THE CORE SKILL that you have to develop as a surgeon.
You have to know when to operate and when not to operate. There is no substitute for clinical experience, and the heterogeneity of clinical conditions makes a one-size-fits-all approach impossible.
Almost all cases benefit from a few hours of preoperative resuscitation before an operation, .....BUT great harm comes from delays in surgery, and reliance on un-necessary imaging tests only available in another hospital! Acute sepsis and ischaemic bowel need surgery within a few hours, not days.
These are some thoughts to guide your decision making.
Need early surgery |
Appendicitis Perforated PU Ischaemic bowel Diffuse peritonitis from any cause |
Can be treated conservatively |
PID Gastritis Cholecystitis Cholangitis Appendicitis* occasionally |
Best with interventional radiology & perc drain |
Diverticular abscess Appendix abscess Liver abscess |
Avoid surgery in these! |
Any “medical cause” of acute abdomen Acute pancreatitis |