mosis, and gastric folds can be seen radiating up to the suture line [66]. A blind pouch of stomach extends above and behind the anastomosis, since the gastric remnant is often sutured to the prevertebral fascia (if the anastomosis is made in the neck) [67]. The closure of the gastric remnant, near the old cardia, leads to mucosal irregularity that can mimic ulceration or even recurrent disease [67]. The stapled closure is usually seen along the anterior wall when the patient is imaged in the left posterior oblique position [66]. It extends to the level of the esophagogastric anastomosis (Fig. 2.19). Surgical clips and sutures usually mark the closure line and may make its recognition easier. The closed stapler insertion site is marked by a row of staples along the anterior gastric wall. These do not reach as high as the gastric resection closure line, which lies more posteriorly and to the right when viewed in the

Figure 2.19. Gastric pull-through staple line. Upper GI series reveals the linear filling defect of the staple line that closes the gastric remnant.

frontal projection [66] (Fig. 2.20). Emptying of the stomach is often delayed in the immediate postoperative period. Gastric emptying takes four times as long in patients without a pyloroplasty than in those who have undergone the procedure [68]. This delay is usually alleviated in 3 to 4 weeks [67].

Figure 2.20. Gastric pull-through staple line. Another upper GI series shows the linear filling defect from the gastric stapler insertion site closure.

The pylorus usually straddles the diaphragm, with the duodenal bulb lying intra-abdominally. Because the stomach is placed in the right paravertebral region, contrast has to flow from right to left to transit the diaphragmatic hiatus to reach the abdomen [69]. Therefore, placing the patient semiupright and left posterior oblique aids in the process and evaluation of gastric emptying. The pylorus may be deformed secondary to pyloromyotomy or pyloroplasty [66]. There may be pancreatitis, related to the mobilization of the stomach and/or the duodenum [70].

Examinations performed weeks after the surgery reveal a fully distensible anastomosis without evidence of nodularity. The gastric pull-through appears to be tubular in configuration, with parallel folds. At this time it should empty more promptly [67].

Imaging by CT has a limited role to play in the immediate postoperative course. Anastomotic leaks, swallowing difficulties including aspiration, stricture, and emptying problems are all best evaluated by routine contrast studies. Evaluation of the neck and mediastinum for abscess and other fluid collections following esophagography is the best indication for CT imaging during this period [69].

With the passage of time, the gastric pull-through undergoes a change in appearance. The mucosal folds are said to become more parallel, and the overall width of the lumen decreases, approximating the appearance of the esophagus [67]. Others have described similar changes in the transplanted colon (see later).

Early postoperative complications are usually related to the esopha-gogastric anastomosis. Leaks at this site are the most commonly encountered problem and are probably underreported [71]. While rates vary considerably from one series to another, Agha et al. reported that pharyngoesophageal anastomoses leaked at a rate almost six times that of cervical esophagogastric ones [67]. Thoracic anastosmoses are even less frequently affected by leaks, perhaps because of tension on the suture line or ischemic changes [71]. Other authors consider all anastomotic leaks to be secondary to faulty technique [70]. Other leaks may develop from underlying diseases, at the other gastric suture or staple lines (closure of the cardia, gastrostomy site for insertion of the stapling device, or staple line for creation of a gastric tube of restricted diameter), or at the point of fixation to the prevertebral fascia [67]. The propensity to leak may be exacerbated by previous gastric surgery and its effect on that organ's vascular supply. Such leaks may be made worse by the bellows effect, associated with the negative intrathoracic pressure and respiratory motion, which sucks luminal contents into the mediastinum. The resultant mediastinitis may cause reflex bronchor-rhea and copious mucus secretions within the lungs [70]. The morbidity of this extravasation is also increased by gastroesophageal reflux.

Incoordination of the swallow mechanism resulted in aspiration in approximately 5% of patients [67]. This is an important factor to consider in choosing the contrast agent to be used, even if an anastomotic leak is not suspected. This aspiration may be related to failure of the cricopharyngeus to properly relax prior to the arrival of a contrast bolus or, following its passage, to close to protect the airway [71,72].

Plain film examination of the chest may be misleading in cases of anastomotic or other suture line disruptions as a chest tube is placed alongside the gastric pull-through and may prevent the accumulation of fluid in the pleural space [66]. Once the chest tube has been removed, any significant reaccumulation of fluid, especially if rapid, may be suspect. If leaks are discovered, follow-up examinations until the leaks are closed are recommended [66,73,74]. Pleural effusions may also be chylous, and secondary to disruption of the thoracic duct, in slightly less than 1% of patients [71]. A disrupted thoracic duct may be difficult to diagnose in the immediate postoperative period. This may occur because the patient is not allowed to eat or drink or is not ingesting a

Figure 2.21. Gastric pull-through. Chest x-ray reveals a soft tissue density, surgical clips, and a linear collection of air in the right hemithorax in the classic appearance of a gastric pull-through.

diet containing fats or lipids. As the diet is advanced, the chylous nature of the pleural fluid may then become apparent. A chylothorax may carry a mortality as high as 50% [70,75,76].

In approximately 75% of patients, the gastric pull-through lies in the midline or to the right of midline in the mediastinum [69,77] (Fig. 2.21). Thus any air seen to the left, especially in the retrocardiac region, is suspect for inadvertent herniation of some abdominal contents into the chest [77] (Fig. 2.22). The differential diagnosis for air in the left

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