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Abstract

Abdominal pain is a relatively common symptom during pregnancy and may be due to anatomical and physiological changes of the pregnant state, such as the ‘round ligament strain’ or may be due to an underlying pathological process. Various obstetric conditions such as placental abruption, clinical chorioamnionitis, threatened pre-term labour and uterine rupture may present with acute abdominal pain. Pregnancy also may predispose to certain clinical conditions such as urinary tract infection that may present with abdominal pain. Conversely, inflammatory or neoplastic processes that are totally unrelated to the pregnant state may first make their presentation during pregnancy, with acute or chronic abdominal pain. Acute abdomen refers to an intra-abdominal process that is characterised by abdominal pain, tenderness and muscular rigidity, for which an emergency surgery must be considered. Life-threatening conditions such as acute appendicitis, acute pancreatitis and intra-peritoneal infection or haemorrhage may result in such an ‘emergency’. It is important to appreciate that pregnancy may alter the clinical presentation of these life-threatening conditions and hence, may ‘mask’ their classical symptoms and signs, delaying the definitive diagnosis. In addition, the presence of a fetus may affect diagnosis and management. Timely diagnosis and appropriate treatment of conditions contributing to abdominal pain and acute abdomen during pregnancy, is essential to improve maternal and perinatal outcome.

 

Keywords

abdominal pain; acute abdomen; acute fatty liver; aortic rupture; appendicitis; cholecystitis; imaging; pancreatitis; red degeneration; torsion
 

Case history

A 32-year-old woman was admitted to the Accident & Emergency (A&E) Department via the London Ambulance Service in her second pregnancy with a history of acute abdominal pain at 16 weeks of gestation. She had collapsed in the ambulance and had needed intensive fluid resuscitation to maintain her vital signs. She had a previous caesarean section at 39 weeks for a breech presentation and was otherwise well with no significant medical or obstetric history. Her condition rapidly deteriorated in the A&E and her vital signs (tachycardia, tachypnoea and falling oxygen saturation), and clinical examination findings (pale, distended abdomen and cold extremities) were suggestive of intra-peritoneal bleeding. An urgent transabdominal scan confirmed massive haemoperitoneum with a viable fetus lying outside the uterus that corresponded to 16 weeks of gestation. Transvaginal scan confirmed an empty endometrial cavity with the presence of a rudimentary horn. She was resuscitated and was immediately transferred to the emergency operating theatre for an urgent laparotomy. A ruptured rudimentary uterine horn with massive haemoperitoneum was noted (Figure 1). An intact fetus (16 weeks-sized) was removed from abdominal cavity (Figure 2).

 

       
       

 

 

The patient was transferred to the Intensive Treatment Unit (ITU) and made a good post-operative recovery.

 

Rational approach to ‘abdominal pain’ in pregnancy

Abdominal pain or discomfort is a common symptom during pregnancy and the vast majority of women do not have any significant intra-abdominal pathology. A requirement of strong analgesics to control pain and/or worsening pain or clinical condition should alert the clinician to explore rare causes and to seek multi-disciplinary input early.

 

The above case illustrates a rare but potentially life threatening cause of acute abdominal pain during the early second trimester of pregnancy. Rupture of a rudimentary horn could occur later than 12 weeks of gestation as the fetus has ‘more room’ to grow prior to the rupture, as compared to a tubal ectopic pregnancy. Young and fit pregnant women generally compensate very well to ongoing hypoxic or hypovolemic insults. However, due to increased vascularity of the uterine horn, the rate of blood loss into the peritoneal cavity following a rupture would be far greater than that would be expected for a ruptured tubal ectopic pregnancy. Therefore, patients may very rapidly deteriorate and may go into a hypovolemic shock, if not actively resuscitated. Hence, it is essential to capture the ‘narrow clinical window of opportunity’ prior to rapid deterioration to improve maternal outcomes. In this case, consideration of the history as well as the site, type and nature of the abdominal pain (Tables 1 and 2), evidence of hypovolemic shock on clinical examination, and urgent ultrasound scan findings that confirmed an extra-uterine pregnancy and massive haemoperitoneum, all helped the attending staff to reach the diagnosis. A multi-disciplinary approach with senior input to treat the specific cause, as well as effective communication in an emergency, ensured that an immediate laparotomy to arrest ongoing haemorrhage was performed. Table 1 illustrates the identification of possible causes based on localisation of pain.

 

 

         

 

         
     

          

 

Effect of pregnancy on the diagnosis of underlying pathology

In pregnancy there are with anatomical, physiological and biochemical changes that may alter classical symptoms and signs that would be normally associated with various clinical conditions. Table 2 illustrates ‘classical’ clinical signs that are described to identify underlying intra-abdominal pathology. However, it is not always possible to elicit these signs during pregnancy as the expansion of gravid uterus may displace intra-abdominal organs from their normal anatomical sites and also may displace the bowel and omentum cranially. This may lead to the loss of protective effect by the ‘abdominal policeman’ (omentum) to localise and limit the infection. A classic example of such ‘masking’ of infection is acute appendicitis during pregnancy. As the pregnancy advances, the uterus may displace the appendix cranially. As a consequence, the classical tenderness around the ‘McBurney's point’ may be absent in late pregnancy and a woman with acute appendicitis may present with pain in the upper abdomen. Moreover, the usual signs of peritonitis (tenderness, guarding, rigidity and rebound tenderness) may not be elicited as the large gravid uterus lies underneath the parietal peritoneum of the anterior abdominal wall, and may protect the parietal peritoneum from ‘irritation’ by the inflamed intra-abdominal organ.

 

The increased plasma volume observed during pregnancy, coupled with changes in the plasma proteins, increased renal clearance and altered hepatic metabolism, may pose difficulties with the interpretation of biochemical markers of pathological conditions. Physiological leucocytosis and raised alkaline phosphatase that are associated with normal pregnancy may also contribute to diagnostic difficulty.

 

Lastly, clinicians may delay imaging techniques such as abdominal X-ray, Magnetic resonance imaging (MRI) or computerised tomography (CT scan) to avoid exposing the fetus to irradiation or due to technical difficulties. Although, there is a fear of teratogenesis in the first trimester and a possible link to childhood cancers with late fetal exposure to ionising radiation, exposures of less than 0.05 Gy have not been associated with pregnancy loss or fetal malformations. Table 3 shows estimated exposure resulting from common radiological investigations.

 

        

 

Common ‘pathological’ causes of abdominal pain during pregnancy and their management

Abdominal pain during pregnancy may be caused by underling obstetric (e.g. placental abruption), gastro-intestinal (e.g. appendicitis), urogenital (e.g. pyelonephritis, torsion of ovarian cysts), inflammatory (inflammatory bowel disease), thrombo-embolic (pelvic venous thrombosis), musculo-skeletal (symphysis pubis diathesis) or extra-abdominal (aortic dissection, myocardial infarction) conditions. Table 4 illustrates common causes of abdominal pain, their usual mode of onset, and suggested investigations based on the differential diagnoses.

 

        
        

 

Common obstetric conditions during late pregnancy that may present with ‘acute abdominal pain’

Any condition during pregnancy that over-distends the uterus, disrupts the normal anatomy of the genital tract or results in inflammatory damage is likely to present with abdominal pain.

 

Placental abruption

Placental abruption refers to premature separation of a normally situated placenta. Painful uterine bleeding is the classical presenting symptom and in severe placental abruption, there may be symptoms and signs of hypovolemic shock. In a concealed abruption, vaginal bleeding may be absent. However, the abdominal pain is often severe and the uterus may be tense and tender, due to the irritation of the myometrium. The fetal heart rate may be absent in severe abruption due to acute uteroplacental insufficiency. Haemodynamic parameters may be out of proportion to the ‘visible’ blood loss. Placental abruption is a clinical diagnosis and should be suspected if a woman presents with acute abdominal pain and vaginal bleeding, as ultrasound may not be a reliable tool in early stages of abruption. Management involves maternal resuscitation (airway, breathing and circulation), correction of hypovolemia and coagulation abnormalities, as well as delivery. Caesarean section should be considered if there is evidence of fetal compromise, once the mother is stabilised. If the fetus is dead or if the woman is in established labour with no evidence of fetal compromise, artificial rupture of membrane and oxytocin infusion may be commenced.

 

Placental ‘perforation’

The incidence of morbidly adherent placentas, especially placental percreta is increasing with rising caesarean section rates. Uterine perforation may occur at any time during pregnancy by the invading placenta. Patients may present with acute abdominal pain and, depending on degree of haemoperitoneum, symptoms and signs of haemorrhagic shock. Figure 1 illustrates uterine rupture with placental perforation. Immediate laparotomy is indicated.

 

Acute polyhydramnios

Presentation is typically with acute abdominal pain, associated with breathlessness due to sudden over-distension of the uterus and splinting of the diaphragm by the enlarged uterus. Clinical signs include a ‘shiny skin’, tense and tender uterus, a ‘fluid thrill’ and difficulty in palpating fetal parts due to increased amniotic fluid volume. Adequate analgesia and ultrasound-guided drainage of the amniotic fluid may help relieve pain and breathlessness.

 

Uterine scar dehiscence

Spontaneous rupture of a non-scarred uterus is a rare entity in modern obstetric practice. Grand multiparity with obstructed labour and injudicious use of oxytocin may predispose to this condition. A previous caesarean section scar may rupture during pregnancy (particularly with a classical or upper segment scar) or most commonly, during labour (lower uterine segment scar). Placenta percreta may also present with uterine rupture in earlier gestation. Patients often present with acute abdominal pain, especially in between uterine contractions, vaginal bleeding and symptoms and signs of hypovolemic shock. Shoulder tip pain may be experienced if significant haemoperitoneum is present, due to irritation of the diaphragm (i.e. referred pain through phrenic nerve). On abdominal examination, tenderness (‘scar tenderness’), guarding, rigidity and rebound tenderness (due to irritation of the peritoneum by blood in the peritoneal cavity) may be noted. Rarely, if the fetus is in the peritoneal cavity, fetal parts may be easily felt and the uterine shape may be asymmetrical. During labour, the most reliable sign of uterine rupture is evidence of fetal compromise on a cardiotocograph (CTG). A vaginal examination may reveal a ‘receding presenting part’ and evidence of intrapartum bleeding. Management involves immediate maternal resuscitation (airway, breathing and circulation) and immediate laparotomy to deliver the fetus and the placenta and to control ongoing haemorrhage and to repair ‘ruptured’ uterus. If successful repair is not possible due to significant damage to the myometrium or its vascularity (previous classical caesarean section, rupture of a multigravid uterus) a peripartum hysterectomy may be necessary.

 

Acute chorioamnionitis

This potentially life-threatening condition presents with acute abdominal pain that may be associated with fever and offensive vaginal discharge and rarely with septic shock. A history suggestive of premature rupture of membranes (PROM) or invasive procedures (amniocentesis, cordocentesis or fetal surgery) may help to establish a diagnosis. On general examination, signs of sepsis (pyrexia, tachypnoea and tachycardia) may be noted and abdominal examination may reveal a tender uterus with evidence of peritonism (guarding, rigidity and rebound tenderness). A speculum examination may confirm purulent vaginal discharge with absence of amniotic membranes. Vaginal swabs and blood cultures may reveal offending organisms. Management involves aggressive treatment of sepsis with broad-spectrum antibiotics and fluids to maintain renal perfusion, as well as expedition of delivery to remove the focus of infection.

 

HELLP syndrome

Haemolysis, Elevated Liver enzymes and Low Platelets (HELLP) syndrome often arises as a complication of pre-eclampsia. However, in about 20% of women, HELLP syndrome may be the first presentation of pre-eclampsia. Acute right upper abdominal pain or epigastric pain, nausea and vomiting are the typical presenting symptoms. A patient with HELLP syndrome may be acutely ill with altered consciousness or irritability with a raised blood pressure. On abdominal examination, tenderness on the right hypochondrium or epigastrium may be elicited. Blood investigations may be suggestive of haemolysis (abnormal peripheral smear with schistocytes, burr cells, raised lactate dehydrogenase >500 u/l and raised bilirubin level >12 mg/l), raised liver enzymes (alanine transaminase over 70 u/L) and low platelets (<100,000/mm3).

 

Management of HELLP syndrome is aimed at immediate maternal stabilisation by controlling blood pressure, prevention of seizures and correction of coagulation abnormality. Once the patient is stabilised, steps should be taken to deliver the fetus. Rarely, distension of the Glisson's capsule of the liver may cause hepatic rupture leading to acute upper abdominal pain and haemorrhagic shock. This life-threatening condition necessitates an emergency laparotomy with repair of liver laceration, ‘abdominal packing’ to control bleeding and correction of coagulation abnormalities.

 

Acute fatty liver in pregnancy (AFLP)

This very rare condition occurs in late pregnancy with an estimated incidence of 1 in 7000 to 1 in 11000 births. The exact aetiology is unknown but is believed to arise secondary to alterations in biochemical and endocrine changes or to an altered immunological response that occurs during pregnancy. It may occur in association with pre-eclampsia and is reported to have high maternal (18%) and fetal (47%) mortality. Classical symptoms include abdominal pain associated with malaise, nausea, vomiting, jaundice and fever. Pain is often in the right upper quadrant of the abdomen and is described as ‘dull aching’. There may be a rapid deterioration of clinical condition with hypoglycaemia, renal failure, disseminated intravascular coagulation (DIC) and hepatic encephalopathy. Abdominal ultrasound examination may help to exclude biliary tract pathology and may confirm alteration of hepatic structure and/or haemorrhage. The role of MRI and CT scans is limited. The diagnosis should be suspected on clinical grounds. Abnormal liver function tests (raised conjugated hyperbilirubinaemia, alkaline phosphate, alanine transaminase, deranged clotting screen), low blood sugar, leucocytosis and thrombocytopenia may be noted. A liver biopsy is not indicated. As this condition is ‘pregnancy-induced’, management involves immediate admission, maternal stabilisation and delivery of the fetus, as well as multi-disciplinary care.

 

Pre-term labour

Pre-term labour often presents with abdominal pain that is described as intermittent and progressive and associated with uterine contractions. On abdominal examination, uterine contractions may be palpable and vaginal examination may confirm changes in the cervix (effacement and dilatation). Management involves excluding chorioamnionitis as a cause of pre-term labour, the use of tocolytics to relax the uterine myometrium and corticosteroids to effect fetal lung maturation.

 

Conditions associated with, but not caused by pregnancy

Pregnancy may increase the pre-disposition to certain inflammatory conditions that may arise as a consequence of the normal anatomical, physiological, hormonal and biochemical changes that are observed during pregnancy.

 

Urinary tract infections (UTI)

The incidence of urinary tract infections are increased during pregnancy secondary to dilatation of the pelvicalyseal system by the relaxing effect of progesterone coupled with possible mechanical effect due to compression of the ureters by the fetal head. This may result in stasis of urine and infection. Escherichia coli (E. coli) accounts for 70–90% of uncomplicated UTIs during pregnancy. It is estimated that up to 20–30% untreated asymptomatic bacteriuria may progress to acute pyelonephritis, usually at end of 2nd or early 3rd trimester. Infection of the bladder (cystitis) often presents with acute supra-pubic pain, nausea, vomiting and fever. On examination, supra-pubic tenderness may be noted. However, if the infection involves the upper urinary tract (ureters and kidneys), patients may become acutely ill. Classical symptoms include acute abdominal (loin to groin) pain, fever, chills, rigours and vomiting. A pyrexia, if present, is often greater than 103 °F (39.4 °C). In such cases, a diagnosis of pyelonephritis should be considered, as failure to institute timely and appropriate treatment may result in septicaemia.

 

Abdominal examination may reveal tenderness over the renal angles (loin or ‘flank’ tenderness). Analysis of mid stream urine and blood samples for culture and antibiotic sensitivity, to exclude infection, should be carried out. Anti-inflammatory agents and intravenous antibiotics are required in the treatment of pyelonephritis. Rarely, rapid spread of infection may result in a perinephric abscess, which may occur due to a delay in diagnosis, inappropriate treatment or in the presence of immunocompromised state such as diabetes mellitus. Perinephric abscess and consequent septicaemia are potentially life threatening and hence necessitate aggressive treatment with broad spectrum intravenous antibiotics and surgical drainage of the abscess.

 

Acute cholecystitis

Acute cholecystitis refers to an inflammation of the gall bladder. Hormonal changes associated with pregnancy result in decreased drainage of bile, delayed emptying time and increased synthesis of cholesterol. All of these predispose to biliary stasis and secondary inflammation or infection.

 

Cholecystitis may also occur secondary to gall stones and it is estimated that up to 3–4% of pregnant women may have asymptomatic pre-existing gall stones. The presence of chronic haemolytic conditions such as sickle cell disease may also predispose to gall stones. Classical symptoms include right upper quadrant pain, which may radiate to the back, nausea, vomiting, jaundice and fever. On examination, icterus may be noted and tenderness may be elicited over the right hypochondrium, which may mimic an acute appendicitis in third trimester. Murphy's sign (tenderness over the tip of the right costal margin on deep inspiration) is elicited in the non-pregnant state but may be absent during pregnancy. Abdominal ultrasound is valuable in demonstrating a distended gall bladder and may also help to identify gall stones. Leucocytosis and a raised alkaline phosphatase may be noted, whereas, alanine transaminase is normal and this may help to differentiate cholecystitis from hepatitis. Management involves intravenous fluids to correct electrolyte imbalance, analgesics and anti-inflammatory agents, naso-gastric suction and the use of intravenous antibiotics. Recurrent attacks of cholecystitis and complications such as empyema or perforation warrant surgical treatment. Percutaneous drainage of the abscess may be indicated. Laparoscopic cholecystectomy during pregnancy has been described.

 

Abdominal pain due to gynaecological conditions

Rapid growth and expansion of the uterus during pregnancy may predispose to torsion of ovarian cysts or a pedunculated fibroid. It has been reported that 20% of adnexal torsions occur during pregnancy, which is suggestive that pregnancy may predispose to torsion. Adnexal torsion is most common in late first trimester, early second trimester and during immediate postpartum period and is rare during the third trimester. This is most likely due to rapid changes in the uterine size during early pregnancy, and during the puerperium, as well as the roominess of the abdominal cavity during this time for the adnexal pathology (ovarian cyst or pedunculated fibroid) to undergo torsion. During the third trimester, due the presence of the large gravid uterus, the available space is not often sufficient for torsion and hence the adnexae remain relatively ‘fixed’. The commonest ovarian mass that undergoes torsion is a dermoid cyst (probably due to its weight) and adnexal torsion occurs more frequently on the right than on the left, by a ratio of 3:2. Ovarian cysts or pedunculated fibroids may be detected during routine dating or anomaly scans and this may facilitate earlier diagnosis of torsion when a woman presents with acute abdominal pain. Other ‘cyst accidents’ (rupture, haemorrhage or torsion) need to be considered in the differential diagnosis. However, the definitive management is emergency exploratory laparotomy; as the adnexa may not be freely accessible through a supra-pubic transverse incision during late pregnancy, a midline or paramedian incision should be considered. Care should be taken to ensure minimal handling of the uterus during the procedure, so as to prevent irritation of the myometrium that may predispose to pre-term labour.

 

Red degeneration of fibroids is common during pregnancy, secondary to associated changes in endocrine and clotting systems. Classical signs/symptoms include acute abdominal pain, nausea, vomiting and mild pyrexia with tenderness on palpation. An ultrasound scan may reveal large cystic spaces within the fibroid, with echo-dense and echo-lucent areas suggestive of degenerative changes. Red degeneration is usually self-limiting and requires a sympathetic approach with reassurance, adequate analgesics and appropriate fluid management. Some women may require opioid analgesics for pain control.

 

Rupture of the rectus abdominis muscle

Rupture of the rectus abdominis muscle is a rare complication during pregnancy and presents with acute abdominal pain during late pregnancy. It is often precipitated by expulsive coughing and occurs predominantly in multigravidae. The underlying aetiology is believed to be secondary to repeated stretching of the rectus abdominis muscle during previous pregnancies, leading to its weakness. Management is conservative with analgesics, however, if a resulting haematoma expands, suggestive of continued bleeding, surgical exploration and ligation of bleeding vessels may be required.

 

Acute abdominal pain due to causes that are unrelated to pregnancy

A woman may present with acute abdominal pain or acute abdomen due to various intra and extra-abdominal pathology that are unrelated to pregnancy. However, anatomical, physiological and biochemical changes observed with pregnancy may mask classical symptoms and signs, leading to increased maternal morbidity ands mortality.

 

Acute appendicitis

Acute appendicitis is the most common pregnancy--unrelated surgical emergency during pregnancy. It is estimated to occur in about 1:2000 pregnancies and though the incidence is similar to the non-pregnant population, the morbidity and mortality is increased during pregnancy, with perforation occurring in about 25% of patients.

 

This high incidence of perforation is due to a delay in diagnosis and treatment, as well as to possible altered immunological response during pregnancy. A patient may present with acute abdominal pain, nausea, vomiting, anorexia or alteration in bowel habits. Abdominal pain in the first trimester may be localised to the McBurney's point, as in the non-pregnant state. However, due to the upward and lateral displacement of the appendix by enlarging gravid uterus, pain is often felt in the umbilical and right hypochondrial regions, in second and third trimesters, respectively.

 

On examination, tenderness may also be elicited as above. Rovsing's sign (pain at the McBurney's point when pressure is exerted over the descending colon) can usually be elicited in pregnant patients. Guarding and rigidity are often present during pregnancy. However, all these classical symptoms and signs may be absent or altered during pregnancy, leading to a delay in the diagnosis. Complications include perforation and peritonitis as well as formation of an appendicular abscess.

 

Leucocytosis associated with pregnancy may pose a diagnostic difficulty. However, predominant neutrophilia (>80%) would support the diagnosis, so would a raised C-reactive protein (CRP), serum amylase, ultrasound and abdominal X-ray. If appendicitis is suspected clinically, surgical management is indicated, despite the possibility of a negative laparotomy. This is justified in view of increased maternal and perinatal morbidity and mortality, if the diagnosis is delayed or missed. Laparoscopic appendicectomy has also been reported during pregnancy. Due to the shift in the anatomical position of the appendix, the grid-iron muscle splitting incision may only be suitable in the first trimester. In late pregnancy, a midline or paramedian incision is recommended, especially if exact cause of abdominal pain is not known prior to surgery. Alternatively, an incision may be made at the point of maximum tenderness.

 

Acute pancreatitis

This is a rare but a potentially life-threatening condition with an incidence between 1 in 1000 to 1 in 10,000 pregnancies. Classical presentation includes sudden onset of acute abdominal pain, mainly confined to the epigastrium, often associated with nausea, vomiting, low grade fever and jaundice. Pain often radiates to the back and is relieved by leaning forward. Predisposing factors include gall stones (commonest), chronic alcohol use, hyperlipidaemia, viral infections, hyperparathyroidism and rarely, abdominal trauma. On examination, epigastric tenderness may be elicited. However, signs of peritoneal irritation are rare due to the gravid uterus separating the parietal peritoneum of the anterior abdominal wall from the inflamed pancreas. Abdominal ultrasound examination may help confirm gall stones and exclude other causes of acute abdominal pain. Elevated serum amylase may help clinch the diagnosis. The pancreas has exocrine and endocrine functions and is involved in carbohydrate metabolism. Therefore, it is vital to recognise that hyperglycemia, hypocalcemia and disturbance of electrolyte balance may also be associated with acute pancreatitis. Although unrecognised and untreated pancreatitis may be associated with increased maternal and perinatal morbidity and mortality, it is generally a self-limiting illness. Supportive treatment with intravenous fluids, correction of electrolyte imbalance, glucose levels, serum calcium levels and keeping the patient nil by mouth, form the mainstay of treatment. In severe disease, naso-gastric suction and total parenteral nutrition may need to be considered. Rarely, if the condition deteriorates, emergency surgery may be indicated to remove gall stones.

 

Acute hepatitis

Acute viral or drug-induced hepatitis may present with abdominal pain, nausea, vomiting, malaise, lethargy, low grade fever and jaundice during pregnancy. A detailed history should be taken to identify the aetiology (history of travel – infective hepatitis, blood transfusion – hepatitis B and C, drug intake – hepatotoxicity). On examination, tenderness in the right hypochondrium can be often elicited. Raised liver enzymes (alanine transaminase) and hepatitis serology (to exclude or to confirm viral infection), as well as an abdominal ultrasound scan, may help in the diagnosis. Treatment is supportive with correction of hypoglycaemia and coagulation disturbances.

 

Peptic ulcer disease

Peptic ulceration is rare in pregnancy and many women with pre-existing peptic ulcer disease often go into remission during pregnancy. However, increased intra-abdominal pressure and the displacement of the gastro-oesophageal junction, coupled with the relaxation of the lower oesophageal sphincter, may cause ‘gastric reflux’, leading to ‘heartburn’. Pain is often localised in