gastric outlet obstruction
TRANSCRIPT
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GASTRIC OUTLET OBSTRUCTION
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DEFINITION
Gastric outlet obstruction (GOO) represents a clinical and pathophysiological consequence of any disease process which produces mechanical impediment to gastric emptying
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CausesTwo well-defined groups of causes—
Benign & Malignant
In the past-- peptic ulcer disease more prevalent, benign causes most common BUT IN RESOURCE CHALLENGED COUNTRIES WHERE IT MAY STILL BE THE COMMONEST CAUSE
Now-- only 37% have benign disease and the remaining have obstruction secondary to malignancy
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Etiology Major benign causes of gastric outlet
obstruction (GOO) are---
PUD
gastric polyps
ingestion of caustics
pyloric stenosis
congenital duodenal webs
gallstone obstruction (Bouveret syndrome)
pancreatic pseudocysts
and bezoars
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Etiology(Contd) Pancreatic cancer is the most common malignancy causing
GOO
Outlet obstruction may occur in 10-20%
Ampullary cancer
Duodenal cancer
Cholangiocarcinomas
Gastric cancer
Metastases to the gastric outlet by other primary tumors
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Pathogenesis
Intrinsic or extrinsic obstruction of the pyloric channel or duodenum
Depends upon the underlying etiology
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Obstruction of the stomach
Hypertrophy of the stomach
Dilatation
Gastritis & depressed acid secretion
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Metabolic effects Dehydration and electrolyte abnormalities-- Increase in
BUN and creatinine are late features of dehydration
Prolonged vomiting causes loss of hydrochloric acid & produces an increase of bicarbonate in the plasma to compensate for the lost chloride-------hypokalemic hypochloremic metabolic alkalosis
Alkalosis shifts the intracellular potassium to the extracellular compartment, and the serum potassium is increased factitiously
With continued vomiting, the renal excretion of potassium increases in order to preserve sodium
The adrenocortical response to hypovolemia intensifies the exchange of potassium for sodium at the distal tubule, with subsequent aggravation of the hypokalemia
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Paradoxically acidic urine
Initially, the urine has a low chloride and high bicarbonate content, reflecting the primary metabolic abnormality
This bicarbonate is excreted along with sodium and so, with time, the patient becomes progressively hyponatraemic and more profoundly dehydrated.
Because of the dehydration, a phase of sodium retention follows and potassium and hydrogen are excreted in preference.
This results in the urine becoming paradoxically acidic.
Alkalosis leads to a lowering of the circulating ionised calcium, and tetany can occur.
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Clinical features
Nausea and vomiting are the cardinal symptoms
Vomiting -- Nonbilious, and it characteristically contains undigested food particles
Early stages --- vomiting intermittent and usually occurs within 1 hour of a meal
Very often it is possible to recognise foodstuff taken several days previously
Pt. loses weight, appears unwell & dehydrated
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Clinical features(Contd)
GOO from a duodenal ulcer or incomplete obstruction typically present with symptoms of-----------
Gastric retention, including early satiety, bloating or epigastric fullness, indigestion, anorexia, nausea, vomiting, epigastric pain, and weight loss
Frequently malnourished and dehydrated and have a metabolic insufficiency
Weight loss , most significant with malignant disease
Abdominal pain is not frequent and usually relates to the underlying cause, eg, PUD, pancreatic cancer
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Examination
Chronically ill looking
Wasted
Dehydrated
may be pale due either to a bleeding ulcer, malignancy
Shock
Epigastric / Rt hypochondrial tenderness
Distended abdomen
Visible gastric peristalsis
Succussion splash
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PRINCIPLES OF MANAGEMENT .
Guiding Principles lies in the recognition of GOO as an emergency, as such, GOAL of treatment include:
-1)Resuscitation/stabilization.;-2)Relieve obstruction;-3)Patient selection/categorization; - patient related factors-4)Offer definitive curative care; - Lesion related factors-5)Prevent recurrence/Follow up care.
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Management Involves
Correcting the metabolic abnormality &
Dealing with the mechanical problem
Rehydrated with i/v isotonic saline with potassium supplementation/ Ringer’s . Replacing the sodium chloride and water allows the kidney to correct the acid–base abnormality
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investigations
1) Stabilise patient
FBC (anaemia)
SEUCR (hypochloraemia, hypokalaemia,hyponatraemia,elevated Hco3)
BLOOD GASES(metabolic alkalosis)
URINALYSIS (paradoxical aciduria)
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investigation
2)To confirm diagnosis
Plain x-ray of abdomen:shows large gastric shadow and a large amount of gastric fluid.
Gastric aspiration:a wide bore stomach tube is placed early in the morning and the stomach is aspirated of resting juice.if >400ml of juice is obtained a presumptive diagnosis of GOO can be made.
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investigation
Esophagogastroduodenoscopy + biopsy(histology and bacterioloical investigation).
Aim is to visualise the stomach mucosa and any ulcer.
Barium meal:
-markely dilated stomach with a lot of residue
-presence of an ulcer crater
-trifoil deformity of the duodenal cap.
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Indications(Surgery) GOO due to benign ulcer disease may be treated medically
if results of imaging studies or endoscopy determine - acute inflammation and edema are the principle causes (as opposed to scarring and fibrosis, which may be fixed)
If medical therapy -- fails, then surgical
Typically, if resolution or improvement is not seen within 48-72 hours, surgical intervention is necessary
The choice of surgical procedure depends upon the patient's particular circumstances
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In cases of malignant obstruction, weigh the extent of surgical intervention for the relief of GOO against the malignancy's type and extent, as well as the patient's anticipated long-term prognosis
As a guiding principle, undertake major tumor resections in the absence of metastatic disease(in fit pts)
In patients with largely metastatic disease, determine the degree of surgical intervention for palliation in light of the patient's realistic prognosis and personal wishes
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THE CHALLENGES HERE
The commonest cause is chronic PUD
Diagnostic challenge in terms of a CT scan, though can still be done
Laboratory challenge in determining the metabolic anomalies
Best to use Ringer’s for resuscitation as potassium is not easily available
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SUMMARY
In poor resource countries, the best diagnostic modality still remains to be clinical ( non- bilious vomitus within an hour of taking a meal, gastric peristalsis and succution splash)
the availability of PPIs and eradication therapy for H.pyroli has made the incidence of malignancy to be on the rise as the cause of GOO