Incidental diagnosis of situs inversus totalis: a perspective from an emergency department attendance

Abstract

A 30-year-old man of African origin presented to our emergency department (ED) with subjective fever and abdominal pain which started on the day of attendance. Vital signs and systemical examination were within normal limits. As part of his evaluation in ED, a 12-lead electrocardiogram was performed which showed features consistent with dextrocardia later confirmed on a chest X-ray as well. An ultrasound scan of the abdomen was performed which showed mirror imaging of the abdominal viscera, all of which were otherwise structurally normal. A diagnosis of situs inversus totalis was made. The patient’s symptoms resolved with analgesia and he was discharged with advice to follow-up in our hospital’s outpatient department. The diagnosis of situs inversus in the ED is a tricky one to make and most cases of this condition are discovered incidentally, as in our case. The mirror-imaged arrangement of viscera can have implications on the site of localised complaints, the physical examination, future health problems for the patient including anaesthesia risks, chronic lung conditions, cardiac complications and specialised trauma management. This anatomical variation can pose diagnostic challenges in such patients. Based on meticulous examination and readily accessible investigations including X-rays, 12-lead ECG and ultrasound, a timely diagnosis can be made.

Background

Anatomically, the abdominal and thoracic organs are asymmetrically placed in the body. This normal anatomical arrangement is known as situs solitus. Situs inversus is the mirror image of this normal asymmetrical arrangement of organs and is thought to result from embryonic malrotation of the abdominal and thoracic viscera. It can be further subdivided into situs inversus totalis (SIT) or situs inversus with levocardia. SIT is the mirror image placement of the heart (dextrocardia or rightward orientation of the heart) and other visceral organs. In SIT, the left lung is seen in the right hemithorax and the right lung in the left hemithorax. The spleen, stomach, jejunum, descending colon and aorta are on the right, with the liver, gall bladder, ascending bowel and inferior vena cava on the left side of the abdomen. Situs inversus with levocardia, where the cardiac apex remains on the left side is rarer than SIT.

Situs inversus is a hereditary condition with an incidence of 1 in 5000–20 000 births.¹ It has no predilection to gender or race.²

Kartagener described a syndrome characterised by a triad of situs inversus, chronic sinusitis and bronchiectasis. This was later recoined as primary ciliary dyskinesia (PCD) to include genetic and acquired causes of ciliary defects. Almost half of all cases of PCD have situs inversus totalis. Complications from PCD include bronchiectasis, recurrent pneumonias, recurrent otitis media and bronchitis.³

Worth noting, situs inversus totalis is commonly associated with a structurally normal heart in 90%–95% of cases. In contrast, isolated dextrocardia is commonly associated with congenital heart defects in upto 90% of cases.⁴

When the arrangement of abdominal organs is neither normally asymmetric nor mirror-imaged, the resulting phenotype is called situs ambiguous, partial situs inversus or heterotaxy syndrome.⁴ Asplenia and polysplenia syndrome are commonly associated with situs ambiguous.⁵

Case presentation

A 30-year-old man of African origin presented to our emergency department (ED) with complaints of subjective fever and generalised abdominal pain which started on the day of attendance. There was no vomiting or diarrhoea. There was no significant past medical, surgical or family history of note. Contact history with sick people was also negative. His last travel outside the country was 1 year ago to his country of origin in Africa. Social history was also negative for smoking, alcohol or recreational drug use.

Vital signs recorded on initial assessment were within normal limits including a temperature of 36.8°C. Systemical examination was unremarkable.

Investigations

As part of his assessment in ED, blood and urine tests were performed which were all within normal limits. In view of his travel history to Africa, a rapid malaria test was also sent which was Plasmodium falciparum antigen positive. However, subsequent smear specimens and workup for malaria were all negative.

Since the patient also reported a fever in the current COVID-19 pandemic, a COVID-19 PCR test, a chest X-ray and a 12-lead ECG were included as part of the initial work up. The COVID-19 PCR test was negative.

His chest X-ray showed dextrocardia with the cardiac apex in the right hemithorax as shown in figure 1. No lung infiltrates were identified.

Figure 1.

Chest X-ray showing dextrocardia with the cardiac apex in the right hemithorax and the liver shadow below the left hemidiaphragm.

A 12-lead ECG (figure 2) showed typical findings of dextrocardia namely negative QRS wave in Lead I and reversal of R wave progression in the precordial leads that is, the QRS complexes become smaller in size as you move on the chest, right to left, from V1 to V6.

Figure 2.

A 12-lead ECG consistent with dextrocardia showing negative QRS complex in Lead I and reversal of R wave progression in the precordial leads, i.e., the QRS complexes become smaller in size as you move on the chest, right to left, from V1 to V6.

An ultrasound examination of the abdomen was performed. As shown in figure 3, mirror imaging of the aorta and inferior vena cava was demonstrated that is, the aorta is seen on the left of the screen and the inferior vena cava on the right.

Figure 3.

Ultrasound image using curvilinear probe depicting mirror imaging of the aorta and inferior vena cava ti.e., the aorta is seen on the left of the screen and the inferior vena cava on the right.

Outcome and follow-up

On subsequent work up for the positive P. falciparum antigen test, multiple malaria smear specimens were collected and reviewed by an experienced microscopist which were all negative, thus ruling out malaria.

The patient’s symptoms resolved with analgesia and he was discharged with advice to follow-up in our hospital’s outpatient department.

With regards to the new diagnosis of situs inversus, the patient reported this was the first time he had heard of this condition. We reassured him this was probably present since birth and should not be a cause of alarm but he should inform healthcare providers of this condition whenever he seeks medical attention in the future. We also directed him to patient information websites on Genetic and Rare Diseases information center i.e. GARD (https://rarediseases.info.nih.gov) and Orpha.net (https://www.orpha.net/consor/cgi-bin/index.php).

Discussion

The diagnosis of situs inversus has implications that could impact the healthcare needs of patients both in the acute phase of illness and long term as well. As this is a rare condition and since most cases are discovered incidentally as part of unscheduled care, it is important frontline healthcare workers are aware of how to diagnose this condition and the impact this condition may have on their patient’s acute care needs. It is worth noting patients with situs inversus can have a normal life expectancy with no symptoms or disability.^{2 6–10} In isolated dextrocardia, life expectancy is impacted by the nature of the associated congenital heart defect.^{9 10}

As stated earlier, while dextrocardia can be presented with either situs solitus or situs inversus. However, isolated dextrocardia (without situs inversus) is more commonly associated with congenital heart disease.⁴

From an airway management perspective, airway anomalies are generally rare with situs inversus. Choanal atresia and chronic sinusitis may cause problems during nasal intubation, and this route should be avoided. Micrognathia, cleft lip/palate and tracheoesophageal fistula are also associated with situs inversus. During endotracheal intubation, left bronchial placement is a risk as the left main bronchus is more in line with the trachea. While there is no definite preference of choice of anaesthesia, it is recommended where possible regional anaesthetic is used where the motor block does not involve the respiratory muscles.¹ We recommend procedural sedation should only be performed after weighing risks, benefits and expertise available on a case-by-case basis.

Almost half of all cases of PCD have situs inversus totalis. Complications from PCD include bronchiectasis, recurrent pneumonias, recurrent otitis media and bronchitis. In the absence of congenital heart disease, this condition can go relatively unnoticed.³

Often the first suggestion of situs inversus totalis is the presence of dextrocardia on a 12-lead ECG at first medical contact. These features include^{11 12}

• Right axis deviation.

• Global negativity in Lead I.

• Positive QRS complexes with upright P and T waves in lead aVR.

• Reversal of R wave progression in the precordial leads that is, the QRS complexes become smaller in size as you move right to left from V1 to V6.

An important differential to consider when faced with a negative QRS complex in Lead I is lead misplacement, that is, an accidental reversal of the right and left arm electrodes.¹³

Patients with situs inversus share the same risk for coronary artery disease as the general population.¹⁴ Often these patients will have right-sided chest pain and right-sided radiation.¹⁵

In patients with suspecting acute coronary syndrome and situs inversus, limb lead reversal is needed to correct the frontal plane axis so lead aVL is on the right side and aVR is on the left. Also, precordial leads should be placed from the patient’s left to right side so lead V1 is in the left parasternal area and lead V6 is in the right mid-axillary area.

There have been case reports of patients with acute cholecystitis presenting with left upper quadrant pain.¹⁶ Left-sided acute appendicitis is also well described in the literature. Left-sided acute appendicitis poses a diagnostic dilemma and is thought to be due to congenital midgut malrotation, situs inversus totalis or an extremely long appendix.¹⁷ A case of incidentally diagnosed situs inversus was reported in a male with left lower quadrant pain misdiagnosed clinically as acute diverticulitis, with subsequent imaging later revealing acute appendicitis.¹⁸

Situs inversus can also be associated with other abnormalities like duodenal atresia, splenic abnormalities and ectopic kidney.⁶ In the context of penetrating trauma in the chest or abdomen, anatomical variation of the viscera and the adjoining vasculature will result in variations in the injury patterns sustained.²

Reports of situs inversus in the setting of trauma are few. However, when they do present, numerous considerations have to be made. The patterns of injuries present atypically due to reversed anatomy.^19–21 In one case report, a stab wound to the left side of the chest in a patient with dextrocardia averted an injury to the heart or the arch of the aorta.²

Splenic injuries have also been documented in cases of situs inversus some requiring splenectomies.^19–21

Considerations needs to be made when doing the point of care ultrasound particularly when looking at the cardiac, right and left upper quadrant views.^{19 20} Central line insertion and confirmation of placement in emergency situations can be challenging given the complexity of this anatomical variation.^{22 23} Procedures like pericardiocentesis and thoracotomies in this subset of patients are rarely reported in the literature.^{24 25}

Learning points.

• Situs inversus is a rare condition but one that can have significant implications on clinical presentation and management due to mirror imaging of organs. Most are discovered incidentally during unscheduled care due to unrelated symptoms.

• All acute and emergency physicians/practitioners should learn how to recognise dextrocardia on a 12-lead ECG.

• Dextrocardia can be associated with situs inversus. Isolated dextrocardia has a strong association with congenital heart disease.

• When recording a 12-lead ECG in a patient with suspected acute coronary syndrome and situs inversus, limb lead reversal and right-sided precordial leads are needed.

• Remember to consult online resources on genetic and rare diseases like GARD (https://rarediseases.info.nih.gov) and Orpha.net (https://www.orpha.net/consor/cgi-bin/index.php)