What Causes Weight Loss?

Patient Presentation
A 9-week-old female came to clinic for an evaluation of weight loss. She was a full term infant with a birth weight of 2.36 kg, and at her 2 week checkup she was 2.58 kg. She presented to her private physician for her 2 month health maintenance examination and had a weight of 3.2 kg (which was decreased from an urgent care visit) and was referred for further evaluation. She was fed formula 2-3 ounces every 2 hours with one stool/day. Since birth she had a history of dribbling formula from her mouth 1-2 times/day after feeding. Around 4 weeks of age she began to have more “emesis” up to 8-9 times/day that was now forceful and the infant was hungry after these episodes. She had been seen in various urgent care centers, had her formula changed 3 times, and was started on Ranitidine without resolution. Her parents had noted that she appeared to be more tired and was moving less and sleeping more recently. The social history found the parents were married with a 3 year old child who was well. The family history was negative.

The pertinent physical exam showed normal vital signs, height of 53 cm (5% for age), weight of 3.2 kg (50% for 1 month old) and head circumference of 37.5% (25% for age). She looked malnourished and was easily aroused. During feeding she was noted to have a large peristaltic wave and a palpable mass in the epigastric area. The laboratory evaluation showed a sodium of 120 mEq/L, potassium of 2.2 mEq/L, chloride of 70 mEq/L, carbon dioxide of 49 mmol/L, BUN of 12 mg/dL and creatinine of 0.5 mg/dL. She had a normal complete blood count. The radiologic evaluation showed a very large gastric bubble on plain abdominal radiograph, and pyloric stenosis on the ultrasound with a width of 5-6 mm and length of 3.2 cm The diagnosis of pyloric stenosis was made. The patient had her severe dehydration and hypochloremic metabolic alkalosis treated with multiple fluid boluses and additional electrolytes. A nasogastric tube was placed for decompression. After fluid and electrolyte resuscitation, she was taken to the operating room for a pyloromyotomy. She had no complications before or after surgery.

Figure 98 – AP radiograph of the abdomen demonstrates a distended stomach with a peristaltic wave within it, the “caterpillar sign.”

Figure 99 – Sagittal (left) and transverse (right) ultrasound images of the pylorus show the pylorus muscle to be elongated in length (3.2 cm) and thickened in diameter (0.5 cm), the classic findings of pyloric stenosis.
Discussion
Hypertrophic pyloric stenosis is the hypertrophying of the pylorus muscle with subsequent stenosis of the pyloric channel. It usually presents in the 3-12th week of life as forceful or projectile non-bilious emesis. It occurs ~ 2-5 patients/1000 live births, more often in males than females (4;1) and most often in first-born males (30%). The infant often appears hungry after feeding.. It can cause failure to gain normal weight, weight loss, and metabolic abnormalities (classically a hypochloremic, hypokalemia metabolic alkalosis). Classically a small abdominal mass about the size of an olive can be palpated at the mid- to right upper quadrant just lateral to the rectus abdominus muscle. On ultrasound examination, a pyloric muscle thickness of > 4 mm is considered diagnostic. The length of the muscle is variable from 14-20 mm, and pyloric diameter may be between 10-14 mm.

Weight loss is a non-specific symptom that can have multiple easy explanations (e.g. inaccurate measurement, acute dehydration, etc. ), but many others are more insidious (i.e. anorexia, thyroid disease) or ominous (e.g. oncological disease, renal failure, etc.) The symptom of true weight loss is more likely to be caused by organic disease than the symptom of weight gain. It needs a detailed history, physical exam and considered laboratory approach to its evaluation. For young children, failure to thrive or lack of normal physiological growth and development has many overlapping etiologies.

Learning Point

The differential diagnosis of weight loss includes:

• Inaccurate measurement or recording
• Different scales
• Normal for situation
  • Newborn period
  • Weight management
  • Medical treatment e.g. edema
• Improper feeding techniques or beliefs
• Inadequate food
• Chronic disease