Assessment of abdominal pain in pregnancy

Absence of a yolk sac when the mean gestational sac diameter is >13 mm³ suggests a miscarriage. When the mean gestational sac diameter is >18 mm³ and an embryo is not visualised, a miscarriage is likely. Absence of cardiac activity by the time the embryo length is ≥5 mm is also suggestive of a miscarriage.

Necessary to assess the rhesus status of the mother if not yet known. If Rh-negative, RhoGAM should be administered.

Ectopic pregnancy can be excluded by visualising an intrauterine pregnancy, as the occurrence of a heterotopic pregnancy is rare.

Features of an intrauterine pregnancy include a gestational sac at 4.5 to 5 weeks, yolk sac at 5 weeks, or fetal pole with heart movements at 5.5 to 6 weeks.

Presence of an empty uterus in association with an adnexal mass is suggestive of an ectopic pregnancy. However, the diagnosis is inconclusive if the uterus is empty and no adnexal mass is present (pregnancy of unknown location). In this scenario the differential includes viable early pregnancy, spontaneous miscarriage, or ectopic pregnancy. Clinicians should rely on the beta-hCG discriminatory cut-off zone.

Fluid in the pouch of Douglas is suggestive of haemoperitoneum.

The presence of a pseudo-gestational sac is observed in approximately 20% of patients with ectopic pregnancy.

A normal intrauterine pregnancy is typically visualised at beta-hCG levels between 1500 and 2500 international units/L (1500 to 2500 milli-international units/mL). If not, the likely differential diagnosis is ectopic pregnancy or miscarriage.

Serial beta-hCG measurement is usually used when the ultrasound is inconclusive and the initial beta-hCG is below the discriminatory zone: 1500 to 2000 international units/L (1500 to 2000 milli-international units/mL). An increase of at least 66% in 2 measurements over 48 hours is suggestive of a viable intrauterine pregnancy. An increase of <66% is suggestive of an ectopic pregnancy. A rapid and steady decline is indicative of a miscarriage.

A single serum measurement cannot exclude ectopic pregnancy or predict the risk of rupture unless it is <5 international units/L (<5 milli-international units/mL).

Necessary to assess the rhesus status of the mother if not yet known. If Rh-negative, RhoGAM should be administered.

To assess presence of uterine contractions as well as fetal hypoxia.

Uni-locular cystic mass of <5 cm suggests low risk for ovarian malignancy. Complex multi-locular cystic mass with thin septations suggests intermediate risk for ovarian malignancy, whereas a solid mass with nodules, thick septations and a size of >5 cm is regarded as high risk for ovarian malignancy.

Use during the first trimester is not recommended, as the effect of MRI on fetal development is unclear.

Gadolinium-based contrast should be avoided and administered only if essential, when the potential benefit to the patient or fetus clearly outweighs the possible but unknown risk of fetal exposure.[47]ACR Committee on Drugs and Contrast Media. ACR manual on contrast media. 2021 [internet publication]. https://www.acr.org/Clinical-Resources/Contrast-Manual

Clinical significance is reduced, as CA-125 is slightly elevated in normal pregnancy.

Pyuria, bacteriuria, and haematuria all suggest cystitis.

A bacterial count of >10² colony-forming units (CFU)/mL of urine in a symptomatic patient is diagnostic of an infection.

These fetal heart patterns are indicative of fetal hypoxia. The presence of uterine contractions on cardiotocography should raise the index of suspicion.

Useful in determining the degree of concealed haemorrhage.

Performed as a baseline investigation. Abnormal if disseminated intravascular coagulation present: elevated INR/PTT and fibrinogen degradation products; decreased fibrinogen.

Although ultrasound is a safe and useful tool in assessing bleeding in pregnancy, its sensitivity is poor and not all abruptions are detected. However, it does assist in excluding other causes of bleeding, such as placenta previa.

Necessary to assess the rhesus status of the mother if not yet known.

Frequently performed in women with abruption to assess the level of fetal-maternal haemorrhage in Rh-negative mothers. Limited use in aiding diagnosis.

May suggest fetal hypoxia or demise, although variable and late decelerations occur before the onset of fetal bradycardia.

Essential to check current haemoglobin status and assess degree of haemorrhage.

Performed as baseline investigation. Abnormal if disseminated intravascular coagulation present: elevated INR/PTT and fibrinogen degradation products; decreased fibrinogen.

A positive leukocyte esterase test and the presence of WBC >10 cells per HPF indicates and confirms pyuria, respectively, and therefore suggests pyelonephritis. In addition to the above, the presence of white cell casts is also a strong indicator of pyelonephritis. Positive nitrites suggest bacteriuria to be confirmed by urine culture.

Bacteriuria is confirmed, Escherichia coli being the predominant pathogen.

Anaemia (Hb <100 g/L [<10 g/dL]) occurs in up to 25% of women.[20]Sheffield JS, Cunningham FG. Urinary tract infection in women. Obstet Gynecol. 2005 Nov;106(5 Pt 1):1085-92. http://www.ncbi.nlm.nih.gov/pubmed/16260529?tool=bestpractice.com An elevated WBC count indicates infection.

Bacteraemia is present in approximately 20% of patients with pyelonephritis.[20]Sheffield JS, Cunningham FG. Urinary tract infection in women. Obstet Gynecol. 2005 Nov;106(5 Pt 1):1085-92. http://www.ncbi.nlm.nih.gov/pubmed/16260529?tool=bestpractice.com

Haematuria is suggestive of nephrolithiasis and is present in 95% of patients, whereas pyuria indicates a stone or infection.[53]Stothers L, Lee LM. Renal colic in pregnancy. J Urol. 1992 Nov;148(5):1383-7. http://www.ncbi.nlm.nih.gov/pubmed/1433534?tool=bestpractice.com A urine pH of 4.7 suggests infection and pH 5.5 suggests a uric acid stone.

Presence of bacteria ≥10² colony-forming units (CFU)/mL suggests a concomitant UTI.

Detects dilatation but not the extent and level of obstruction. It is difficult to visualise the ureters and intra-ureteric calculi.

Suggestive of systemic infection.

Creatinine >124 micromol/L (>1.4 mg/dL) and urea >7.14 mmol/L (>20 mg/dL) is suggestive of azotaemia due to ureteric obstruction.

Differentiates between physiological and obstructive dilatation, but cannot visualise the actual stone.

May reveal severe hydronephrosis and hydro-ureters.

A positive leukocyte esterase test indicates pyuria, suggesting the presence of infection or a stone, as does a urine pH of 4.7 and 5.5, respectively. Haematuria (presence of blood >2/mm³) is present in 95% of patients with nephrolithiasis.

Presence of bacteria ≥10² colony-forming units (CFU)/mL suggests a concomitant UTI.

A complex mass appearance suggests a ruptured haemorrhagic cyst surrounded by a haematoma. Fluid in the pouch of Douglas is also indicative of a ruptured cyst.

The internal echo pattern depends on the stage of haemorrhage and the amount of fluid within the cyst. A sponge-like, lace-like, or reticular pattern within the cyst is classic and suggests haemorrhage. A crenated appearance of the wall also suggests haemorrhage; as the cyst resolves, the wall collapses on itself. Fluid in the pouch of Douglas indicates haemoperitoneum.

Necessary to assess anaemia.

Strongly suggestive of ovarian torsion.

Suggestive of ovarian torsion. Can help determine whether the flow in the ovary is impaired. However, specificity is poor.

Although the WBC count may be elevated, there is no correlation between leukocyte count and tissue necrosis. Anaemia may develop in sub-acute presentations.

Suggestive of appendicitis. The position of the appendix in the abdomen changes as the pregnancy advances. Appendix is assessed by graded compression technique with a linear transducer.[54]Lim HK, Bae SH, Seo GS. Diagnosis of acute appendicitis in pregnant women: value of sonography. AJR. 1992 Sep;159(3):539-42. http://www.ncbi.nlm.nih.gov/pubmed/1503019?tool=bestpractice.com  Its visualisation can be challenging due to large body habitus and increased uterine size, particularly during the second and third trimester.[55]Katz DS, Klein MA, Ganson G, et al. Imaging of abdominal pain in pregnancy. Radiol Clin North Am. 2012;50(1):149-71. http://www.ncbi.nlm.nih.gov/pubmed/22099493?tool=bestpractice.com Therefore, the sensitivity and the specificity of this diagnostic tool vary significantly across different studies, widely ranging from 20% to 100% and 80% to 100%, respectively.​[54]Lim HK, Bae SH, Seo GS. Diagnosis of acute appendicitis in pregnant women: value of sonography. AJR. 1992 Sep;159(3):539-42. http://www.ncbi.nlm.nih.gov/pubmed/1503019?tool=bestpractice.com [55]Katz DS, Klein MA, Ganson G, et al. Imaging of abdominal pain in pregnancy. Radiol Clin North Am. 2012;50(1):149-71. http://www.ncbi.nlm.nih.gov/pubmed/22099493?tool=bestpractice.com ​​[56]Barloon TJ, Brown BP, Abu-Yousef MM, et al. Sonography of acute appendicitis in pregnancy. Abdom Imaging. 1995 Mar-Apr;20(2):149-51. http://www.ncbi.nlm.nih.gov/pubmed/7787719?tool=bestpractice.com [57]Cobben LP, Groot I, Haans L, et al. MRI for clinically suspected appendicitis during pregnancy. AJR Am J Roentgenol. 2004 Sep;183(3):671-5. http://www.ncbi.nlm.nih.gov/pubmed/15333354?tool=bestpractice.com [58]Israel GM, Malguria N, McCarthy S, et al. MRI vs. ultrasound for suspected appendicitis during pregnancy. J Magn Reson Imaging. 2008 Aug;28(2):428-33. http://www.ncbi.nlm.nih.gov/pubmed/18666160?tool=bestpractice.com [59]Pedrosa I, Lafornara M, Pandharipande PV, et al. Pregnant patients suspected of having acute appendicitis: effect of MR imaging on negative laparotomy rate and appendiceal perforation rate. Radiology. 2009 Mar;250(3):749-57. http://www.ncbi.nlm.nih.gov/pubmed/19244044?tool=bestpractice.com [Figure caption and citation for the preceding image starts]: The site of the appendix changes as pregnancy advancesChamberlain G. ABC of antenatal care: abdominal pain in pregnancy. BMJ. 1991;302:1390-4. Used with permission [Citation ends].

Although leukocytosis is physiological in pregnancy, a persistent WBC count <10 x 10⁹/L (<10,000/microlitre) may give reassurance. A left shift of neutrophils occurs in approximately 75% of patients.[60]Tamir IL, Bongard FS, Klein SR. Acute appendicitis in the pregnant patient. Am J Surg. 1990 Dec;160(6):571-5. http://www.ncbi.nlm.nih.gov/pubmed/2252115?tool=bestpractice.com

MRI abdomen and pelvis without contrast is an appropriate alternative to abdominal ultrasound for the initial imaging of a pregnant woman with right lower quadrant pain with fever, leukocytosis, and suspected appendicitis.[42]American College of Radiology. ACR appropriateness criteria: right lower quadrant pain. 2022 [internet publication]. https://www.acr.org/Quality-Safety/Appropriateness-Criteria It has a sensitivity of 91.8% and specificity of 97.9% for the diagnosis of acute appendicitis in pregnant women with clinically suspected appendicitis.[23]Kave M, Parooie F, Salarzaei M. Pregnancy and appendicitis: a systematic review and meta-analysis on the clinical use of MRI in diagnosis of appendicitis in pregnant women. World J Emerg Surg. 2019;14:37. https://www.doi.org/10.1186/s13017-019-0254-1 http://www.ncbi.nlm.nih.gov/pubmed/31367227?tool=bestpractice.com

Gadolinium-based contrast should be avoided and administered only if essential, when the potential benefit to the patient or fetus clearly outweighs the possible but unknown risk of fetal exposure.[47]ACR Committee on Drugs and Contrast Media. ACR manual on contrast media. 2021 [internet publication]. https://www.acr.org/Clinical-Resources/Contrast-Manual

If the ultrasound examination is negative, a CT scan may be considered.[61]Lazarus E, Mayo-Smith WW, Mainiero MB, et al. CT in the evaluation of nontraumatic abdominal pain in pregnant women. Radiology. 2007 Sep;244(3):784-90. http://www.ncbi.nlm.nih.gov/pubmed/17709829?tool=bestpractice.com

As with plain film x-rays, CT scan should only be considered if the risk of maternal morbidity and mortality outweighs the risk of fetal radiation exposure. This cautious approach has led to the development of evidence-based guidelines to support physicians in the evaluation of risks and benefits, which should always be considered and discussed with patients prior to their implementation.​[44]American College of Obstetricians and Gynecologists. Committee opinion, no. 723: guidelines for diagnostic imaging during pregnancy and lactation. Oct 2017 [internet publication]. https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2017/10/guidelines-for-diagnostic-imaging-during-pregnancy-and-lactation

Gallstones are usually present in >95% of patients with acute cholecystitis.[62]Chang T, Lepanto L. Ultrasonography in the emergency setting. Emerg Med Clin North Am. 1992 Feb;10(1):1-25. http://www.ncbi.nlm.nih.gov/pubmed/1732090?tool=bestpractice.com

Of limited value as leukocytosis is usually observed in normal pregnancy.

Of limited value as elevated levels of alkaline phosphatase are usually observed in normal pregnancy, and liver enzymes not elevated in all cases.

Transiently present in 33% of patients.[63]Hiatt JR, Hiatt JC, Williams RA, et al. Biliary disease in pregnancy: strategy for surgical management. Am J Surg. 1986 Feb;151(2):263-5. http://www.ncbi.nlm.nih.gov/pubmed/3511761?tool=bestpractice.com

MRI is the preferred test when ultrasound scan is inconclusive, as it can be used to evaluate the entire biliary system without exposing the patient to ionising radiation.[65]American College of Radiology. ACR Appropriateness Criteria® right upper quadrant pain. 2022 [internet publication]. https://acsearch.acr.org/docs/69474/Narrative

Gadolinium-based contrast should be avoided and administered only if essential, when the potential benefit to the patient or fetus clearly outweighs the possible but unknown risk of fetal exposure.[47]ACR Committee on Drugs and Contrast Media. ACR manual on contrast media. 2021 [internet publication]. https://www.acr.org/Clinical-Resources/Contrast-Manual

Use serum lipase testing in preference to serum amylase.[28]Tenner S, Vege SS, Sheth SG, et al. American College of Gastroenterology guidelines: management of acute pancreatitis. Am J Gastroenterol. 2024 Mar 1;119(3):419-37. https://journals.lww.com/ajg/fulltext/2024/03000 american_college_of_gastroenterology_guidelines_.14.aspx http://www.ncbi.nlm.nih.gov/pubmed/38857482?tool=bestpractice.com Serum lipase levels remain raised for longer (up to 14 days after symptom onset vs. 5 days for amylase), providing a higher likelihood of picking up the diagnosis in patients with a delayed​ presentation.[66]Rompianesi G, Hann A, Komolafe O, et al. Serum amylase and lipase and urinary trypsinogen and amylase for diagnosis of acute pancreatitis. Cochrane Database Syst Rev. 2017 Apr 21;4(4):CD012010. https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD012010.pub2/full http://www.ncbi.nlm.nih.gov/pubmed/28431198?tool=bestpractice.com

About one quarter of people with acute pancreatitis fail to be diagnosed as having acute pancreatitis with serum amylase and serum lipase tests.[66]Rompianesi G, Hann A, Komolafe O, et al. Serum amylase and lipase and urinary trypsinogen and amylase for diagnosis of acute pancreatitis. Cochrane Database Syst Rev. 2017 Apr 21;4(4):CD012010. https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD012010.pub2/full http://www.ncbi.nlm.nih.gov/pubmed/28431198?tool=bestpractice.com [67]Avanesov M, Löser A, Keller S, et al. Diagnosing acute pancreatitis-clinical and radiological characterisation of patients without threefold increase of serum lipase. Eur J Radiol. 2017 Oct;95:278-85. http://www.ncbi.nlm.nih.gov/pubmed/28987680?tool=bestpractice.com

The patient should be admitted and treated as having acute pancreatitis, even if these tests are normal, if there is a suspicion of acute pancreatitis.[66]Rompianesi G, Hann A, Komolafe O, et al. Serum amylase and lipase and urinary trypsinogen and amylase for diagnosis of acute pancreatitis. Cochrane Database Syst Rev. 2017 Apr 21;4(4):CD012010. https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD012010.pub2/full http://www.ncbi.nlm.nih.gov/pubmed/28431198?tool=bestpractice.com

About 1 in 10 patients without acute pancreatitis may be wrongly diagnosed as having acute pancreatitis with these tests.[66]Rompianesi G, Hann A, Komolafe O, et al. Serum amylase and lipase and urinary trypsinogen and amylase for diagnosis of acute pancreatitis. Cochrane Database Syst Rev. 2017 Apr 21;4(4):CD012010. https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD012010.pub2/full http://www.ncbi.nlm.nih.gov/pubmed/28431198?tool=bestpractice.com [ ] What is the accuracy of serum amylase and lipase for the diagnosis of acute pancreatitis?/cca.html?targetUrl=https://www.cochranelibrary.com/cca/doi/10.1002/cca.3092/fullShow me the answer​​ It is important to consider other conditions that require urgent surgery, even if these tests are abnormal.[66]Rompianesi G, Hann A, Komolafe O, et al. Serum amylase and lipase and urinary trypsinogen and amylase for diagnosis of acute pancreatitis. Cochrane Database Syst Rev. 2017 Apr 21;4(4):CD012010. https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD012010.pub2/full http://www.ncbi.nlm.nih.gov/pubmed/28431198?tool=bestpractice.com

The diagnostic performance of these tests decreases with time, and additional investigations should be performed if there is a suspicion of acute pancreatitis.[66]Rompianesi G, Hann A, Komolafe O, et al. Serum amylase and lipase and urinary trypsinogen and amylase for diagnosis of acute pancreatitis. Cochrane Database Syst Rev. 2017 Apr 21;4(4):CD012010. https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD012010.pub2/full http://www.ncbi.nlm.nih.gov/pubmed/28431198?tool=bestpractice.com

Suggestive of acute pancreatitis.

Hypertriglyceridaemia is a rare cause of pancreatitis, but may account for up to 56% of cases of acute pancreatitis in pregnancy.[28]Tenner S, Vege SS, Sheth SG, et al. American College of Gastroenterology guidelines: management of acute pancreatitis. Am J Gastroenterol. 2024 Mar 1;119(3):419-37. https://journals.lww.com/ajg/fulltext/2024/03000 american_college_of_gastroenterology_guidelines_.14.aspx http://www.ncbi.nlm.nih.gov/pubmed/38857482?tool=bestpractice.com [29]Yang AL, McNabb-Baltar J. Hypertriglyceridemia and acute pancreatitis. Pancreatology. 2020 Jul;20(5):795-800. http://www.ncbi.nlm.nih.gov/pubmed/32571534?tool=bestpractice.com ​

Abdominal imaging is not needed for diagnosis in most patients. However, once a diagnosis of acute pancreatitis has been made, transabdominal ultrasound is required to rule out gallstones as the aetiology.[28]Tenner S, Vege SS, Sheth SG, et al. American College of Gastroenterology guidelines: management of acute pancreatitis. Am J Gastroenterol. 2024 Mar 1;119(3):419-37. https://journals.lww.com/ajg/fulltext/2024/03000 american_college_of_gastroenterology_guidelines_.14.aspx http://www.ncbi.nlm.nih.gov/pubmed/38857482?tool=bestpractice.com

MRI is preferred for pregnant women.[45]American College of Radiology. ACR appropriateness criteria​: acute pancreatitis. 2019 [internet publication]. https://acsearch.acr.org/docs/69468/Narrative ​ CT scan to be considered only when severe necrosis of the pancreas is suspected.

MRI is preferred to CT scan in pregnancy.[45]American College of Radiology. ACR appropriateness criteria​: acute pancreatitis. 2019 [internet publication]. https://acsearch.acr.org/docs/69468/Narrative

The American College of Gastroenterology guidelines recommend CT or MRI after 48-72 hours in patients who do not improve or whose symptoms worsen.[28]Tenner S, Vege SS, Sheth SG, et al. American College of Gastroenterology guidelines: management of acute pancreatitis. Am J Gastroenterol. 2024 Mar 1;119(3):419-37. https://journals.lww.com/ajg/fulltext/2024/03000 american_college_of_gastroenterology_guidelines_.14.aspx http://www.ncbi.nlm.nih.gov/pubmed/38857482?tool=bestpractice.com ​ Other guidelines recommend a delay of 72-96 hours after symptom onset before contrast-enhanced CT or MRI to assess for necrosis.[68]Leppäniemi A, Tolonen M, Tarasconi A, et al. 2019 WSES guidelines for the management of severe acute pancreatitis. World J Emerg Surg. 2019 Jun 13;14:27. https://wjes.biomedcentral.com/articles/10.1186/s13017-019-0247-0 http://www.ncbi.nlm.nih.gov/pubmed/31210778?tool=bestpractice.com ​​[69]Working Group IAP/APA acute pancreatitis guidelines. IAP/APA evidence-based guidelines for the management of acute pancreatitis. Pancreatology. 2013 Jul-Aug;13(4 suppl 2):e1-15. https://www.sciencedirect.com/science/article/pii/S1424390313005255?via%3Dihub http://www.ncbi.nlm.nih.gov/pubmed/24054878?tool=bestpractice.com ​​

MRI employing MRCP has the advantage of not requiring intravenous contrast or radiation, although intravenous gadolinium enhances images compared with non-contrast MRI.

In addition, MRCP allows better visualisation of common bile duct stones and the pancreatic duct compared with CT. It can more readily distinguish solid from cystic in dealing with peripancreatic collections.[45]American College of Radiology. ACR appropriateness criteria​: acute pancreatitis. 2019 [internet publication]. https://acsearch.acr.org/docs/69468/Narrative

Increases the likelihood of diagnosis.

Of limited value as leukocytosis is usually observed in normal pregnancy.

Plain abdominal sequential films may be needed if the diagnosis is unclear. Considered only if risk of maternal morbidity and mortality outweighs the risk of fetal radiation exposure.

Diagnoses and monitors fibroids during pregnancy and determines their relative position to the placenta. Doppler ultrasound can demonstrate vessel splaying around the fibroids and so differentiate between fibroids and myometrial thickening. An echodense or echolucent appearance suggests a degenerating myoma.

Interpretation of these results must take into account the effect of the physiological changes of pregnancy.

Essential to monitor fetal heart rate and establish the presence of fetal hypoxia.

Useful in assessing fetal wellbeing.

Thrombocytopenia and haemolytic anaemia are typical features.

May act as an indicator for haemolysis. However, an elevated value may also reflect hepatocyte destruction.

Performed as baseline investigation. Abnormal if disseminated intravascular coagulation present: elevated INR/PTT and fibrinogen degradation products; decreased fibrinogen.

Elevated liver enzymes are a typical feature.

Proteinuria is seen in almost all patients.

Suggestive of an acute sub-capsular hepatic haematoma.

AST can be elevated up to 500 units/L compared with 60 units/L in pre-eclampsia, and 150 units/L in haemolysis, elevated liver enzymes, and low platelet count (HELLP) syndrome.

Patients often have a persistent leukocytosis.

A common entity in acute fatty liver of pregnancy.

Primarily used to exclude other diagnoses.

Volume depletion may result in haemoconcentration and thus an elevated haematocrit.

Useful in assessing osmotic pressure.

To assess hyponatraemia.

Baseline investigation to exclude coagulopathy.

To determine ovarian size and presence of ascites.

Considered when patients present with signs of respiratory distress. Risk of maternal morbidity and mortality should outweigh the risk of fetal radiation exposure.

Indicated if pericardial effusion is suspected.

There may be evidence of fetal distress or demise.

To assess the presence of extensive intra-abdominal fluid and haemoperitoneum.

Is usually confirmatory, but should be reserved for cases where diagnosis is unclear due to the risk of fetal radiation exposure.

It may provide useful information regarding the size and location of the mass.

May occur in the presence of a large haematoma.