MRI use has become increasingly common for diagnosis of appendicitis in children and pregnant patients due to the radiation dosage that, while of nearly negligible risk in healthy adults, can be harmful to children or the developing fetus. In pregnancy, it has been found to be more useful during the second and third trimester, particularly as the enlargening uterus displaces the appendix, making it difficult to find by ultrasound. The periappendiceal stranding that is reflected on CT by fat stranding on MRI appears as increased fluid signal on T2 weighted sequences. First trimester pregnancies are usually not candidates for MRI, as the fetus is still undergoing organogenesis, and there are no long-term studies to date regarding its potential risks or side effects.

Ultrasonography and doppler sonography are useful to detect appendicitis, especially in children. Ultrasound can show free fluid collection in the right iliac fossa, along with a visible appendix with increased blood flow when using color Doppler, and noncompressibility of the appendix, as it is essentially a walled off abscess. Other secondary sonographic signs of acute appendicitis include the presence of echogenic mesenteric fat surrounding the appendix and the acoustic shadowing of an appendicolith. In some cases (approximately 5%), ultrasonography of the iliac fossa does not reveal any abnormalities despite the presence of appendicitis. This false negative finding is especially true of early appendicitis before the appendix has become significantly distended. In addition, false negative findings are more common in adults where larger amounts of fat and bowel gas make visualizing the appendix technically difficult. Despite these limitations, sonographic imaging in experienced hands can often distinguish between appendicitis and other diseases with similar symptoms. Some of these conditions include inflammation of lymph nodes near the appendix or pain originating from other pelvic organs such as the ovaries or Fallopian tubes.

Stable patients presenting to A&E (accident and emergency department) or ER (emergency room) with severe abdominal pain will almost always have an abdominal x-ray and/or a CT scan. These tests can provide a differential diagnosis between simple and complex pathologies. However, in the unstable patient, fluid resuscitation and a FAST-ultrasound are done first, and if the latter is positive for free fluid, straight to surgery. They may also provide evidence to the doctor whether surgical intervention is necessary.

Patients will also most likely receive a complete blood count (or full blood count in the U.K.), looking for characteristic findings such as neutrophilia in appendicitis.

Traditionally, the use of opiates or other painkillers in patients with an acute abdomen has been discouraged before the clinical examination, because these would alter the examination. However, the scientific literature does not reveal any negative results from these alterations.

On x-rays, gas may be visible in the abdominal cavity. Gas is easily visualized on x-ray while the patient is in an upright position. The perforation can often be visualised using computed tomography. White blood cells are often elevated.

A laparoscopy or laparotomy can also be performed to visually confirm an ectopic pregnancy. This is generally reserved for women presenting with signs of an acute abdomen and/or hypovolemic shock. Often if a tubal abortion or tubal rupture has occurred, it is difficult to find the pregnancy tissue. A laparoscopy in very early ectopic pregnancy rarely shows a normal looking fallopian tube.

Culdocentesis, in which fluid is retrieved from the space separating the vagina and rectum, is a less commonly performed test that may be used to look for internal bleeding. In this test, a needle is inserted into the space at the very top of the vagina, behind the uterus and in front of the rectum. Any blood or fluid found may have been derived from a ruptured ectopic pregnancy.

Progesterone levels of less than 20 nmol/l have a high predictive value for failing pregnancies, whilst levels over 25 nmol/l are likely to predict viable pregnancies, and levels over 60 nmol/l are strongly so. This may help in identifying failing PULs that are at low risk and thereby needing less follow-up. Inhibin A may also be useful for predicting spontaneous resolution of PUL, but is not as good as progesterone for this purpose.

In addition, there are various mathematical models, such as logistic regression models and Bayesian networks, for the prediction of PUL outcome based on multiple parameters. Mathematical models also aim to identify PULs that are "low risk", that is, failing PULs and IUPs.

Dilation and curettage is sometimes used to diagnose pregnancy location with the aim of differentiating between an EP and a non-viable IUP in situations where a viable IUP can be ruled out. Specific indications for this procedure include either of the following:

- no visible IUP on transvaginal ultrasonography with a serum hCG of more than 2000 IU/ml

- an abnormal rise in hCG level. A rise of 35% over 48 hours is proposed as the minimal rise consistent with a viable intrauterine pregnancy.

- an abnormal fall in hCG level, such as defined as one of less than 20% in 2 days

Most women with a PUL are followed up with serum hCG measurements and repeat TVS examinations until a final diagnosis is confirmed. Low-risk cases of PUL that appear to be failing pregnancies may be followed up with a urinary pregnancy test after 2 weeks and get subsequent telephone advice. Low-risk cases of PUL that are likely intrauterine pregnancies may have another TVS in 2 weeks to access viability. High-risk cases of PUL require further assessment, either with a TVS within 48 h or additional hCG measurement.

Various modalities of diagnosis are available:

- Cystoscopy

- Colonoscopy

- Poppy seed test

- Transabdominal ultrasonography

- Abdominopelvic CT

- MRI

- Barium enema

- Bourne test

- Cystogram

A definite algorithm of tests is followed for making the diagnosis.

A diagnosis of peritonitis is based primarily on the clinical manifestations described above. Rigidity (involuntary contraction of the abdominal muscles) is the most specific exam finding for diagnosing peritonitis (+ likelihood ratio: 3.9). If peritonitis is strongly suspected, then surgery is performed without further delay for other investigations. Leukocytosis, hypokalemia, hypernatremia, and acidosis may be present, but they are not specific findings. Abdominal X-rays may reveal dilated, edematous intestines, although such X-rays are mainly useful to look for pneumoperitoneum, an indicator of gastrointestinal perforation. The role of whole-abdomen ultrasound examination is under study and is likely to expand in the future. Computed tomography (CT or CAT scanning) may be useful in differentiating causes of abdominal pain. If reasonable doubt still persists, an exploratory peritoneal lavage or laparoscopy may be performed. In patients with ascites, a diagnosis of peritonitis is made via paracentesis (abdominal tap): More than 250 polymorphonucleate cells per μL is considered diagnostic. In addition, Gram stain is almost always negative, whereas culture of the peritoneal fluid can determine the microorganism responsible and determine their sensitivity to antimicrobial agents.

Surgical intervention is nearly always required in form of exploratory laparotomy and closure of perforation with peritoneal wash. Occasionally they may be managed laparoscopically.

Conservative treatment including intravenous fluids, antibiotics, nasogastric aspiration and bowel rest is indicated only if the person is nontoxic and clinically stable.

Fetal and neonatal bowel obstructions are often caused by an intestinal atresia, where there is a narrowing or absence of a part of the intestine. These atresias are often discovered before birth via an ultrasound, and treated with using laparotomy after birth. If the area affected is small, then the surgeon may be able to remove the damaged portion and join the intestine back together. In instances where the narrowing is longer, or the area is damaged and cannot be used for a period of time, a temporary stoma may be placed.

Diagnosis is guided by the person's presenting symptoms and laboratory findings. The gold standard imaging modality for the presence of gallstones is ultrasound of the right upper quadrant. There are many reasons for this choice, including no exposure to radiation, low cost, and availability in city, urban, and rural hospitals. Gallstones are detected with a specificity and sensitivity of greater than 95% with ultrasound. Further signs on ultrasound may suggest cholecystitis or choledocholithiasis. Computed Topography (CT) is not indicated when investigating for gallbladder disease as 60% of stones are "not" radiopaque. CT should only be utilized if other intraabdominal pathology exists or the diagnosis is uncertain. Endoscopic retrograde cholangiopancreatography (ERCP) should be used only if lab tests suggest the existence of a gallstone in the bile duct. ERCP is then both diagnostic and therapeutic.

Right upper quadrant abdominal ultrasound is most commonly used to diagnose cholecystitis. Ultrasound findings suggestive of acute cholecystitis include gallstones, fluid surrounding the gallbladder, gallbladder wall thickening (wall thickness over 3 mm), dilation of the bile duct, and sonographic Murphy's sign. Given its higher sensitivity, hepatic iminodiacetic acid (HIDA) scan can be used if ultrasound is not diagnostic. CT scan may also be used if complications such as perforation or gangrene are suspected.

In normal conditions, the peritoneum appears greyish and glistening; it becomes dull 2–4 hours after the onset of peritonitis, initially with scarce serous or slightly turbid fluid. Later on, the exudate becomes creamy and evidently suppurative; in dehydrated patients, it also becomes very inspissated. The quantity of accumulated exudate varies widely. It may be spread to the whole peritoneum, or be walled off by the omentum and viscera. Inflammation features infiltration by neutrophils with fibrino-purulent exudation.

The main diagnostic tools are blood tests, X-rays of the abdomen, CT scanning, and/or ultrasound. If a mass is identified, biopsy may determine the nature of the mass.

Radiological signs of bowel obstruction include bowel distension and the presence of multiple (more than six) gas-fluid levels on supine and erect abdominal radiographs.

Contrast enema or small bowel series or CT scan can be used to define the level of obstruction, whether the obstruction is partial or complete, and to help define the cause of the obstruction.

According to a meta-analysis of prospective studies by the Cochrane Collaboration, the appearance of water-soluble contrast in the cecum on an abdominal radiograph within 24 hours of oral administration predicts resolution of an adhesive small bowel obstruction with a pooled sensitivity of 97% and specificity of 96%.

Colonoscopy, small bowel investigation with ingested camera or push endoscopy, and laparoscopy are other diagnostic options.

In someone suspected of having cholecystitis, blood tests are performed for markers of inflammation (e.g. complete blood count, C-reactive protein), as well as bilirubin levels in order to assess for bile duct blockage. Complete blood count typically shows an increased white blood count (12,000–15,000/mcL). C-reactive protein is usually elevated although not commonly measured in the United States. Bilirubin levels are often mildly elevated (1–4 mg/dL). If bilirubin levels are more significantly elevated, alternate or additional diagnoses should be considered such as gallstone blocking the common bile duct (common bile duct stone). Less commonly, blood aminotransferases are elevated. The degree of elevation of these laboratory values may depend on the degree of inflammation of the gallbladder.

In many cases, RLP is confused with other conditions that cause abdominal pain. Described below are some problematic diagnoses related to RLP.

- RLP and appendicitis

A 22-year-old pregnant woman presenting abdominal pains was initially diagnosed with RLP and was discharged. Subsequent symptoms and further tests revealed acute non-perforated appendicitis that required surgery. Appendectomy was successful but premature labor occurred 7 days after discharge, leading to spontaneous abortion.

- RLP and inguinal hernia

Several cases of varicosity, of the round ligament during pregnancy leading to RLP have been reported although they were frequently misdiagnosed as inguinal hernia.

In one case, a woman in the 28th week of gestation developed a lump in the left pubic area. The swelling was prominent when standing but not in the supine position and has a cough impulse. Ultrasonography revealed varicosities on the uterine round ligament.

In another case, a woman at 22 weeks gestation was diagnosed with inguinal hernia and underwent surgery. Explorative surgery did not locate a hernia but revealed varicosities of the round ligament. Resection of the uterine ligament was successfully performed and no perinatal and postpartum complications were reported.

- Postpartum RLP

Several cases of postpartum RLP have been reported. In one case, a 27-year-old woman presented with abdominal pain 24 hours after normal vaginal delivery. Another case was that of a 29-year-old woman who presented with RLP 3 days after delivery. In both cases, initial diagnosis was inguinal hernia. In the first case, emergency surgery did not locate any hernia but found the round ligament of the uterus to be edematous and filled with thrombosed varicose veins. The thrombosed part was excised and the patient recovered without sequelae.

Another case report described a 37-year-old woman presenting with inguinal mass 6 days after normal vaginal delivery. CT and MRI revealed thrombosed blood vessels along the inguinal course of the uterine round ligament that extended towards the labia majora.

- RLP and endometriosis

Several cases of inguinal endometriosis, that infiltrates the round ligament of the uterus have been reported in fertile, non-pregnant women. In the majority of these cases, diagnosis was problematic. In some cases, definitive diagnosis of round ligament endometriosis was only possible during exploratory surgery.

- RLP and myoma

Cases of myoma-like growth occurring on the uterine round ligament have been reported.

- RLP and IVF

Gonadotropin stimulation during in vitro fertilization can induce cyst development in certain parts of the female reproductive system. A case report documented the development of a mesothelial cyst on the uterine round ligament of a woman after IVF stimulation.

Hydrosalpinx may be diagnosed using ultrasonography as the fluid filled elongated and distended tubes display their typical echolucent pattern. However, a small hydrosalpinx may be missed by sonography. During an infertility work-up a hysterosalpingogram (HSG), an X-ray procedure that uses a contrast agent to image the fallopian tubes, shows the retort-like shape of the distended tubes and the absence of spillage of the dye into the peritoneum. If, however, there is a tubal occlusion at the utero-tubal junction, a hydrosalpinx may go undetected. When a hydrosalpinx is detected by an HSG it is prudent to administer antibiotics to reduce the risk of reactivation of an inflammatory process.

When laparoscopy is performed, the surgeon may note the distended tubes, identify the occlusion, and may also find associated adhesions affecting the pelvic organs. Laparoscopy not only allows for the diagnosis of hydrosalpinx, but also presents a platform for intervention (see management).

As pelvic inflammatory disease is the major cause of hydrosalpinx formation, steps to reduce sexually transmitted disease will reduce incidence of hydrosalpinx. Also, as hydrosalpinx is a sequel to a pelvic infection, adequate and early antibiotic treatment of a pelvic infection is called for.

Abdominal pains during pregnancy may be due to various pathologies. RLP is one of the most common and benign of these pains. However, diagnosis of RLP is problematic. Some of the conditions that may present symptoms similar to those of RLP are appendicitis, ectopic pregnancy, kidney stones, urinary tract infection, uterine contractions, inguinal hernia, ovarian cysts, and endometriosis. If abdominal pain is continuous and accompanied by vaginal bleeding, excessive vaginal discharge, fever, chills, or vomiting, then it is most unlikely to be RLP and immediate consultation with a health care provider is warranted.

Physical examination, ultrasonography, and blood and urine tests may be able to pinpoint the actual cause of abdominal pain. In some cases, however, RLP was only diagnosed during exploratory surgery.

A number of other causes may produce similar symptoms including appendicitis, ectopic pregnancy, hemorrhagic or ruptured ovarian cysts, ovarian torsion, and endometriosis and gastroenteritis, peritonitis, and bacterial vaginosis among others.

Pelvic inflammatory disease is more likely to reoccur when there is a prior history of the infection, recent sexual contact, recent onset of menses, or an IUD (intrauterine device) in place or if the partner has a sexually transmitted infection.

Acute pelvic inflammatory disease is highly unlikely when recent intercourse has not taken place or an IUD is not being used. A sensitive serum pregnancy test is typically obtained to rule out ectopic pregnancy. Culdocentesis will differentiate hemoperitoneum (ruptured ectopic pregnancy or hemorrhagic cyst) from pelvic sepsis (salpingitis, ruptured pelvic abscess, or ruptured appendix).

Pelvic and vaginal ultrasounds are helpful in the diagnosis of PID. In the early stages of infection, the ultrasound may appear normal. As the disease progresses, nonspecific findings can include free pelvic fluid, endometrial thickening, uterine cavity distension by fluid or gas. In some instances the borders of the uterus and ovaries appear indistinct. Enlarged ovaries accompanied by increased numbers of small cysts correlates with PID.

Laparoscopy is infrequently used to diagnose pelvic inflammatory disease since it is not readily available. Moreover, it might not detect subtle inflammation of the fallopian tubes, and it fails to detect endometritis. Nevertheless, laparoscopy is conducted if the diagnosis is not certain or if the person has not responded to antibiotic therapy after 48 hours.

No single test has adequate sensitivity and specificity to diagnose pelvic inflammatory disease. A large multisite U.S. study found that cervical motion tenderness as a minimum clinical criterion increases the sensitivity of the CDC diagnostic criteria from 83 percent to 95 percent. However, even the modified 2002 CDC criteria do not identify women with subclinical disease.

Upon a pelvic examination, cervical motion, uterine, or adnexal tenderness will be experienced. Mucopurulent cervicitis and or urethritis may be observed. In severe cases more testing may be required such as laparoscopy, intra-abdominal bacteria sampling and culturing, or tissue biopsy.

Laparoscopy can visualize "violin-string" adhesions, characteristic of Fitz-Hugh–Curtis perihepatitis and other abscesses that may be present.

Other imaging methods, such as ultrasonography, computed tomography (CT), and magnetic imaging (MRI), can aid in diagnosis. Blood tests can also help identify the presence of infection: the erythrocyte sedimentation rate (ESR), the C-reactive protein (CRP) level, and chlamydial and gonococcal DNA probes.

Nucleic acid amplification tests (NAATs), direct fluorescein tests (DFA), and enzyme-linked immunosorbent assays (ELISA) are highly sensitive tests that can identify specific pathogens present. Serology testing for antibodies is not as useful since the presence of the microorganisms in healthy people can confound interpreting the antibody titer levels, although antibody levels can indicate whether an infection is recent or long-term.

Definitive criteria include histopathologic evidence of endometritis, thickened filled Fallopian tubes, or laparoscopic findings. Gram stain/smear becomes definitive in the identification of rare, atypical and possibly more serious organisms. Two thirds of patients with laparoscopic evidence of previous PID were not aware they had PID, but even asymptomatic PID can cause serious harm.

Laparoscopic identification is helpful in diagnosing tubal disease; a 65 percent to 90 percent positive predictive value exists in patients with presumed PID.

Upon gynecologic ultrasound, a potential finding is "tubo-ovarian complex", which is edematous and dilated pelvic structures as evidenced by vague margins, but without abscess formation.

Vascular disorders are more likely to affect the small bowel than the large bowel. Arterial supply to the intestines is provided by the superior and inferior mesenteric arteries (SMA and IMA respectively), both of which are direct branches of the aorta.

The superior mesenteric artery supplies:

1. Small bowel

2. Ascending and proximal two-thirds of the transverse colon

The inferior mesenteric artery supplies:

1. Distal one-third of the transverse colon

2. Descending colon

3. Sigmoid colon

Of note, the splenic flexure, or the junction between the transverse and descending colon, is supplied by the most distal portions of both the inferior mesenteric artery and superior mesenteric artery, and is thus referred to medically as a watershed area, or an area especially vulnerable to ischemia during periods of systemic hypoperfusion, such as in shock.

Acute abdomen of the ischemic variety is usually due to:

1. A thromboembolism from the left side of the heart, such as may be generated during atrial fibrillation, occluding the SMA.

2. Nonocclusive ischemia, such as that seen in hypotension secondary to heart failure, may also contribute, but usually results in a mucosal or mural infarct, as contrasted with the typically transmural infarct seen in thromboembolus of the SMA.

3. Primary mesenteric vein thromboses may also cause ischemic acute abdomen, usually precipitated by hypercoagulable states such as polycythemia vera.

Clinically, patients present with diffuse abdominal pain, bowel distention, and bloody diarrhea. On physical exam, bowel sounds will be absent. Laboratory tests reveal a neutrophilic leukocytosis, sometimes with a left shift, and increased serum amylase. Abdominal radiography will show many air-fluid levels, as well as widespread edema.

Acute ischemic abdomen is a surgical emergency. Typically, treatment involves removal of the region of the bowel that has undergone infarction, and subsequent anastomosis of the remaining healthy tissue.

It is unclear whether those experiencing a gallstone attack should receive surgical treatment or not. The scientific basis to assess whether surgery outperformed other treatment was insufficient and better studies were needed as of a SBU report in 2017. Treatment of biliary colic is dictated by the underlying cause. The presence of gallstones, usually visualized by ultrasound, generally necessitates a surgical treatment (removal of the gall bladder, typically via laparoscopy). Removal of the gallbladder with surgery, known as a cholecystectomy, is the definitive surgical treatment for biliary colic. A 2013 Cochrane review found tentative evidence to suggest that early gallbladder removal may be better than delayed removal. Early laparoscopic cholescystectomy happens within 72 hours of diagnosis. In a Cochrane review that evaluated receiving early versus delayed surgery, they found that 23% of those who waited on average 4 months ended up in hospital for complications, compared to none with early intervention with surgery. Early intervention has other advantages including reduced number of visits to the emergency department, less conversions to an open surgery, less operating time required, reduced time in hospital post operatively. The Swedish agency SBU estimated in 2017 that increasing acute phase surgeries could

free multiple in-hospital days per patient and would additionally spare pain and suffering in wait of receiving an operation. The report found that those with acute inflammation of the gallbladder can be surgically treated in the acute phase, within a few days of symptom debut, without increasing the risk for complications (compared to when the surgery is done later in an asymptomatic stage).

A complete history and physical examination can be suggestive, especially if a palpable mass in the right lower quadrant of the abdomen is present (though this can be present in the absence of DIOS). Ultrasound and computed tomography (CT) imaging of the abdomen can confirm the diagnosis by demonstrating dilated loops of intestine with material in the intestinal lumen with bubbles. Air-fluid levels may be seen in those affected by DIOS.

Colic is diagnosed after other potential causes of crying are excluded. This can typically be done via a history and physical exam, and in most cases tests such as X-rays or blood tests are not needed. Babies who cry may simply be hungry, uncomfortable, or ill. Less than 10% of babies who would meet the definition of colic based on the amount they cry have an identifiable underlying disease.

Cause for concern include: an elevated temperature, a history of breathing problems or a child who is not appropriately gaining weight.

"Red flag" indicating that further investigations may be needed include:

- Vomiting (vomit that is green or yellow, bloody or occurring more than 5/day)

- Change in stool (constipation or diarrhea, especially with blood or mucous)

- Abnormal temperature (a rectal temperature less than or over

- Irritability (crying all day with few calm periods in between)

- Lethargy (excess sleepiness, lack of smiles or interested gaze, weak sucking lasting over 6 hours)

- Poor weight gain (gaining less than 15 grams a day)

Problems to consider when the above are present include:

- Infections (e.g. ear infection, urine infection, meningitis, appendicitis)

- Intestinal pain (e.g. food allergy, acid reflux, constipation, intestinal blockage)

- Trouble breathing (e.g. from a cold, excessive dust, congenital nasal blockage, oversized tongue)

- Increased brain pressure (e.g., hematoma, hydrocephalus)

- Skin pain (e.g. a loose diaper pin, irritated rash, a hair wrapped around a toe)

- Mouth pain (e.g. yeast infection)

- Kidney pain (e.g. blockage of the urinary system)

- Eye pain (e.g. scratched cornea, glaucoma)

- Overdose (e.g. excessive Vitamin D, excessive sodium)

- Others (e.g. migraine headache, heart failure, hyperthyroidism)

Persistently fussy babies with poor weight gain, vomiting more than 5 times a day, or other significant feeding problems should be evaluated for other illnesses (e.g. urinary infection, intestinal obstruction, acid reflux).