At What Level Does Elevated Glucose Cause Glucosuria?

Patient Presentation
A 6-year-old female came to clinic with a history of frequent urination. She was toilet trained around 3 years of age during the day, and around 4 years of age at night. Her mother said that she had occasional daytime urinary accidents but over the last week she was having them 2-4 times/day during the day only. The girl denied any dysuria, abdominal pain, voiding small amounts, having problems passing urine or changes in urine color. Her mother was not sure if she was having any dribbling. The patient initially denied but later stated that she was not stooling very often. The past medical history was negative except for one uncomplicated urinary tract infection when she was 4 years old. The family history was negative for kidney disease or diabetes. The review of systems was negative for excessive thirst, polydipsia, or nocturnal enuresis. The family denied any weight loss or changes in how her clothes were fitting.

The pertinent physical exam showed a well-appearing female with normal vital signs. Her growth parameters were in the 75-90% and she had gained weight since her last visit 5 months ago. HEENT was negative including an appropriately sized thyroid gland. Her abdominal examination had palpable stool in the left lower quadrant. Her genitourinary examination was negative. Her back had no skin or spinal defects noted and she had a normal neurological examination.

The resident physician’s differential diagnosis included the diagnosis of constipation causing diurnal enuresis, a urinary tract infection and diabetes. When the attending physician asked why she was concerned about diabetes she said that the inpatient team had recently admitted a younger child who had type 1 diabetes and diabetic ketoacidosis who presented with enuresis. When pressed what else in the history and physical examination lead her to think about diabetes she replied, “I know that this is not that common, but I just worry.” The attending noted that it was always good to be concerned but this child had no other symptoms such as polydipsia, weight changes, other illnesses. “It’s also less likely because the child does not have nocturnal enuresis. Although patients can have intermittent glucosuria causing enuresis, its more likely that they would have enuresis at night too,” the attending noted. The attending then went on, “We’ll get the urinalysis because she has had an UTI in the past plus it will tell us if there is glucosuria. I don’t remember exactly how high the blood glucose has to be before it spills into the urine but it’s fairly high I think.” The laboratory testing of a urinalysis was normal with no ketones, glucose, leukocyte esterase or nitrates. The patient’s clinical course was that she was sent home with instructions for constipation management with followup in 1 month.

Constipation generally is defined as infrequent or painful defecation. Most children develop constipation after the child begins to associate pain (e.g. a hard bowel movement) with defecation. The child then begins to withhold the stools trying to decrease the defecation discomfort. As stool withholding continues, the rectum dilates and gradually accommodates with the normal defecation urge disappearing. Passing large hard stools infrequently reinforces the defecation pain. The cycle continues. If the cycling is severe enough, worsening stool retention and more abnormal defecation dynamics occurs. Chronic rectal distension results in both loss of rectal sensitivity, and loss of urge to defecate, which can lead to encopresis. The differential diagnosis of constipation can be reviewed here.

Constipation can also lead to enuresis because of increased pressure on the bladder and also because of inappropriate toileting behaviors where children infrequently voids as well as defecates. The differential diagnosis of diurnal enuresis can be reviewed here.

Type 1 diabetes mellitis is one of the most common chronic diseases in childhood and is increasing in prevalence worldwide. In childhood the presentation age is bimodal with one peak at 4-6 years and another at 10-14 years. Most studies show no gender differences except for an increase in older adolescent males noted in European studies. The diagnosis is made by a fasting glucose of > 126 mg/dL (7 mmol), or postprandial glucose of > 200 mg/dL (11.1 mmol), or hemoglobin A1c > 6/5% (48 mmol/mol), in addition to insulin deficiency and clinical signs of insulin deficiency (such as those in the classic presentation below).

The presentations of type 1 diabetes includes:

  • Hyperglycemia without acidosis
    • Classic presentation – polyuria, polydipsia and weight loss
    • Polyuria and polydipsia are seen in the vast majority of cases (90%); weight loss occurs in about 1/2 of children. Nocturnal enuresis is a very common early symptom.
    • Symptoms usually have been occurring for 10 days
    • Symptoms can be subtle so a careful history is needed especially in young children where polyuria may be more difficult to identify. Young children may also present with dehydration, abdominal pain, fatigue or a prolonged candidal infection.
    • Patients may appear relatively well
  • Diabetic ketoacidosis
    • Less common presentation (~10%) of patients
    • Similar to classic presentation but patients usually appear more ill
    • May have fruity-smelling breath and mental status changes such as lethargy and drowsiness
  • Occult
    • Patient diagnosed because of family history or tested for other reasons
  • Non-specific symptoms
    • Abdominal pain
    • Emesis
    • Growth retardation
    • Infectious diseases including perineal candidiasis
    • Lethargy
    • Pruritis
    • School or mental problems
    • Visual changes
    • Weakness

Learning Point
The renal glomerulus filters glucose which is reabsorbed by the proximal convoluted tubule.
Polyuria occurs when the serum glucose concentration overwhelms the tubules ability to reabsorb the glucose.
This occurs at serum glucose concentrations above 180 mg/dL (10 mmol/L).

Questions for Further Discussion
1. How does Type 2 diabetes mellitis present?
2. What are risk factors for diabetes mellitus?

Related Cases

To Learn More
To view pediatric review articles on this topic from the past year check PubMed.

Evidence-based medicine information on this topic can be found at, the National Guideline Clearinghouse and the Cochrane Database of Systematic Reviews.

Information prescriptions for patients can be found at MedlinePlus for these topics: Constipation, Diabetes and Diabetes Type 1.

To view current news articles on this topic check Google News.

To view images related to this topic check Google Images.

To view videos related to this topic check YouTube Videos.

Vanelli M, Scarabello C, Fainardi V. Available tools for primary ketoacidosis prevention at diabetes diagnosis in children and adolescents. “The Parma campaign”. Acta Biomed. 2008 Apr;79(1):73-8.

Schultz-Lampel D, Steuber C, Hoyer PF, Bachmann CJ, Marschall-Kehrel D, Bachmann H. Urinary incontinence in children. Dtsch Arztebl Int. 2011 Sep;108(37):613-20.

Merger SR, Leslie RD, Boehm BO. The broad clinical phenotype of Type 1 diabetes at presentation. Diabet Med. 2013 Feb;30(2):170-8.

Levitsky LL, Misra M. Epidemiology, Presentation, and Diagnosis of Type 1 Diabetes Mellitis in Children and Adolescents. UpToDate.
(rev. 6/10/14, cited 7/14/15).

Levitsky LL, Misra M. Complications and Screening in Children and Adolescents with Type 1 Diabetes Mellitis. UpToDate.
(rev. 1/2/2015, cited 7/14/15).


Donna M. D’Alessandro, MD
Professor of Pediatrics, University of Iowa Children’s Hospital