Nausea is the most common symptom in gastroparesis. Other common symptoms include vomiting, early satiety, postprandial fullness, and bloating. Vomitus often contains undigested chewed food. Weight loss and weight gain can be seen. Wide glycemic fluctuations can also happen in gastroparesis [14][15]. The timing of the symptoms in relation to meals is important. Physical examination is usually nonspecific. However, the presence of neuropathy, abdominal distension, halitosis can be seen in patients with diabetic gastroparesis.

Factors that may trigger an exacerbation of diabetic gastroparesis include uncontrolled blood glucose levels, medication noncompliance or intolerance, adrenal insufficiency, and infection.

The first step in the evaluation of patients who present with the symptoms above would be to exclude mechanical obstruction and peptic ulcer disease. All patients should undergo an upper gastrointestinal endoscopy. This should be followed by either a CT scan with oral and intravenous contrast or other imaging such as a small bowel follow-through to exclude obstruction beyond the duodenum. Retained food is seen on endoscopy without mechanical obstruction, and in rare cases, bezoars suggest gastroparesis.

The conventional test that is cost-effective and widely used for the diagnosis of gastroparesis is the measurement of gastric emptying by scintigraphy, which is considered the gold standard by many [16]. Solid-phase emptying is usually used to evaluate for gastroparesis. Liquid-phase emptying is not well demonstrated for diagnosing gastroparesis and is more widely used to assess for dumping syndrome after gastric surgery. Most centers use a 99 mTc sulfur colloid labeled egg white sandwich as the test meal [17]. Standard imaging is performed at 0,1,2,4 hours postprandially. A four-hour study is more sensitive and accurate in the diagnosis of gastroparesis, and a shortened 2- and 3-hour study should be avoided [18][19][16]. Medications such as opiates and anticholinergics can slow gastric motility, whereas prokinetics and other medications can hasten gastric emptying. Hyperglycemia is known to slow gastric motility, and it is worthwhile to try and achieve euglycemia prior to performing the test if that is an option [16]. 

Breath testing is another validated study for gastroparesis. Most commonly, 13C-labelled octanoate, a medium-chain triglyceride, is bound to a solid meal and ingested. After emptying from the stomach, it is absorbed by the small intestine and metabolized to 13CO2, which is expelled from the lungs during respiration. Currently, it has limited penetrance into the clinical practice and is performed for clinical research and pharmaceutical studies[16].

Electrogastrography and gastroduodenal manometry are other tests based on the myoelectrical activity that are potentially helpful tests but are not yet available for widespread clinical use.

The first step in the treatment of symptomatic gastroparesis is often lifestyle modifications. Optimal glycemic control in patients with diabetes will minimize the effects of hyperglycemia, causing delayed gastric emptying. Smaller, more frequent meals with minimizing carbonated beverages, increasing the liquid content, reducing fats, and fiber content are some of the common recommendations[20]. Alcohol and smoking should be discouraged, as they can worsen the symptoms [21][22].

Antiemetics are often the first step in patients with gastroparesis as they help with the common symptoms of nausea and vomiting. Serotonin (5-HT3) receptor antagonists like ondansetron, phenothiazines (dopamine receptor antagonists) like prochlorperazine and promethazine are commonly used. Side effects include sedation and extrapyramidal effects, and therefore, these are usually used on an 'as-needed' basis [16].

The cornerstone of pharmacologic therapy in diabetic gastroparesis consists of prokinetic agents.

Metoclopramide, a 5-HT4 receptor activator and dopamine receptor antagonist in the stomach with weak 5-HT3 receptor antagonism in the nervous system, is a commonly used medication that increases the contraction amplitude of esophageal, fundic, and antral musculature. It is effective for the treatment of gastroparesis for several weeks, but long term dosing has shown inconsistent results [23].

Erythromycin binds to the motilin receptors, which are responsible for the initiation of the MMC in the upper gut [24][25]. Like metoclopramide, erythromycin works well in the short term, but long term loss of response is common.

Domperidone is a dopamine (D2) agonist with effects similar to metoclopramide but is much less likely to cause extrapyramidal side effects as it does not cause the blood-brain barrier. Symptomatic patients with diabetes have reported improvement with domperidone therapy, but again, the effect could be lost in about six weeks [26][27][28]. Domperidone was associated with cardiac arrhythmias in the past and is not FDA approved in the United States. Cisapride is a 5-HT4 agonist that might have effects last up to 1 year, but unfortunately, it was also associated with ventricular arrhythmias, including torsades de pointes, and has been withdrawn from the US market. Both these drugs are available through select investigators as part of clinical trials with strict patient monitoring. In patients who do not respond well to the above therapies alone, combination prokinetic therapies can be tried. Symptomatic control of nausea using antiemetics can also be tried. Several studies have evaluated pyloric botulinum toxin injection, but these studies were often unblinded and had small numbers of patients[16]. 

Gastric electrical stimulation has been studied, but so far, there has not been a significant reduction in symptoms that were noted consistently across various small studies. It was granted humanitarian approval from the FDA for the treatment of chronic refractory nausea, but it is not available widely and not routinely reimbursed [16][29][16]. 

In refractory patients with severe symptoms, a gastrostomy tube for intermittent decompression by venting or suctioning may provide relief [29]. For patients who are not able to maintain nutrition with oral intake, placement of a feeding jejunostomy can be effective for providing nutrition, fluids, electrolytes, and reduce hospitalizations [30][31]. A trial of nasojejunal feeding can predict the response to a jejunostomy [29]

The last resort in refractory gastroparesis if surgery, which can be a partial gastrectomy with Roux-en-Y gastrojejunostomy and gastric resection. There is not enough data on surgical treatment at this time, and the decision to subject a patient to this should ideally be made by a motility expert [16].

Gastric outlet obstruction due to mechanical causes can present with similar symptoms and must be ruled out by endoscopy or imaging studies prior to making a diagnosis of gastroparesis.

The outcomes of diabetic gastroparesis are not well defined. Prognosis depends on the adequate control of hyperglycemia and compliance with medications. It affects the quality of life, and education regarding the need for lifelong management of this condition is essential. 

Malnutrition is an important complication of diabetic gastroparesis that often needs management with jejunostomy, parenteral nutrition, or surgery. Wide glycemic fluctuations can occur in diabetic gastroparesis, and this can lead to complications such as hypoglycemia and diabetic ketoacidosis or hyperosmolar hyperglycemic state. Nausea and vomiting can lead to aspiration and pneumonia from aspiration. 

Patients should be educated regarding the chronic and often irreversible nature of the disease. Adherence to a "gastroparesis diet", judicious use of medications and strict control of hyperglycemia are important patient factors that can change the course of the disease and prevent complications. 

Management of diabetic gastroparesis is extremely challenging. It is best done with an interprofessional team that includes an internist, endocrinologist, diabetes nurse educator, primary care provider, and a gastroenterologist, gastroenterology nurses, and pharmacists. Nurses provide patient education, monitor patients, and facilitate referrals and communication among the team. Pharmacists review prescribed medications, educate patients, and evaluated compliance. [Level 5]

Treatment of diabetic gastroparesis is aimed at alleviating the associated symptoms and replenishing electrolytes, nutrition, and hydration.

Frequently used medications include erythromycin (macrolide antibiotic-associated with increased gastrointestinal motility) and metoclopramide (antiemetic and prokinetic) and polyethylene glycol 3350 may additionally be used to provide relief from severe constipation.

Patients who continue to experience symptoms of gastroparesis despite medical therapy may be candidates for gastric electrical stimulation (GES) wherein an electrical device is implanted into the abdomen.

Unfortunately, no treatment works reliably or consistently. Once the condition has been diagnosed, it is progressive and imparts a very poor quality of life.[32][33]