3 DISCUSSION
Black esophagus, also known as ANE, was first described by Goldenberg et
al. in 1990 (1), and gained prominence after a series of cases were
reported in 2007 (2). AEN has remained a rare diagnosis with an
estimated prevalence of up to 0.28% (3,4). It has an endoscopic finding
characterized by diffuse, circumferential black discoloration of the
mucosa that affects the distal part of the esophagus and stops abruptly
at the gastroesophageal junction (1-4,7,10).
Though the exact etiology of the disease remains unclear, it is presumed
to be multifactorial with ischemia, impaired intrinsic mucosal barriers,
and massive reflux of gastric contents that acutely exceeds the
protective and regenerative properties of vulnerable esophageal mucosa
enabling both ischemic and chemical injury of the esophagus
(3,4,8,11-13). Chronic predisposing conditions and poor nutritional
status may also contribute to decreased mucosal buffering and may
potentiate the mechanisms by which esophageal necrosis is progressed.
Diagnosis of AEN is based on endoscopic findings which consist of a
circumferentially black-appearing esophageal mucosa that abruptly ends
at the gastroesophageal junction and transitions to normal gastric
mucosa (1-4,7,10). Biopsy is supportive and obtained to exclude other
etiologies, but is not required to establish the diagnosis (3,4).
Patients are typically older males with multiple medical comorbidities,
which increase the likelihood of AEN (2-4). Demographically,
hyperglycemia is seen in almost 90% of patients with this condition
(14,15). Moreover, disease associations include vascular compromise,
hypertension, chronic kidney disease, malignancy, malnourishment,
gastric outlet obstruction, and in this case, diabetes mellitus and
alcohol abuse (3,4). The clinical presentation is remarkable for upper
gastrointestinal bleeding, with most patients presenting with
hematemesis or melena, comparable to our case (3,4). Other symptoms may
include abdominal pain, nausea, vomiting, dysphagia, fever, and syncope
(3,4). The patient presented with abdominal pain and nausea. Laboratory
findings are nonspecific, but it has been reported that associated
laboratory abnormalities may include anemia, leukocytosis, and
hyperlactatemia (3,4), all of which are comparable to the patient.
There is no specific therapy for AEN. Management of AEN should be
directed at correcting the underlying medical condition and protective
care with hemodynamic resuscitation, total parenteral nutrition, and the
administration of antacid therapy with aggressive intravenous proton
pump inhibitors (3,4). Enteral feeding is not recommended because of the
risk of perforation unless there is persistent vomiting (3,4,9).
Moreover, prophylactic antibiotics are not necessary. The decision to
initiate antimicrobial therapy should be individualized based on
clinical and objective findings of serious infection (3,4,9,16). The
patient presented no sign of infection. The most common long-term
sequela of AEN is stricture formation, which can complicate up to 10%
of all cases (3,4,9). No stricture formation was shown in our case on
follow-up EGD.
The correlation between DKA and AEN has been described in the literature
(14,17-23). DKA has been reported to be one of the most common
triggering events for AEN (3,4,9). Although the precise mechanism
remains unknown, several pathogenic mechanisms may possibly be
implicated. The presence of long-standing diabetes mellitus predisposes
the patient to the development of atherosclerosis leading to an
increased risk of ischemia (3,4,14,19,24,25). It has been suggested that
poor nutritional status with hemodynamic instability, and hyperglycemia
in DKA can lead to poor vascular flow and an impaired mucosal barrier
from corrosive injury of gastric contents (3,4,8,14,19,24,25). Moreover,
gastric stasis, which can occur in the absence of neuropathy during DAK,
can induce gastroesophageal reflux by which esophageal necrosis is
accelerated (3,4,19). DKA can also result in profound osmotic diuresis
and fluid loss leading to hypoperfusion of the distal esophagus
(3,4,14,18).
In summary, we presented a case of AEN complicating diabetic
ketoacidosis. Though AEN remains a rare cause of upper gastrointestinal
bleeding, it is a potentially life-threatening condition. Notably, up to
9% of patients with DKA have evidence of upper gastrointestinal
bleeding, but less than one-third of those undergo endoscopy to
determine the underlying cause (10). Therefore, a clinician should be
aware of AEN as a potential cause of upper gastrointestinal bleeding
when faced with an elderly, possibly poorly controlled diabetic patient
or when additional significant comorbidities are present.