The rectal method provides the most accurate reflection of a person’s core body temperature, especially in infants and young children under three years old. This measurement is considered the gold standard for accuracy in this age group. While it may seem invasive, proper technique ensures the process is safe and yields reliable data for assessing fever.
Necessary Preparations Before Measurement
Before measurement, prepare both the device and the person. Use a dedicated digital thermometer designed for rectal use, avoiding glass or mercury thermometers. Clean the tip thoroughly with soap and water or an alcohol wipe, then rinse and dry it completely.
The thermometer tip must be lubricated to allow for gentle insertion and minimize discomfort. Apply a small amount of a water-soluble gel or petroleum jelly to the bulb end of the device.
The correct positioning of a child is necessary to ensure stability during the measurement. For infants, you can place them belly-down across your lap or on a firm surface, holding your palm against their lower back to keep them still. Alternatively, you can lay the child on their back and lift their legs toward their chest, resting your free hand against the back of their thighs.
Precise Insertion Depth and Technique
The recommended insertion depth varies based on age to accommodate the person’s size. For infants under six months, the thermometer should be inserted approximately one-half inch, or just until the silver tip is fully covered.
For older infants and children up to three years of age, the depth is between one-half inch and one inch (1.3 to 2.5 centimeters). When inserting the lubricated tip, do so gently and slowly, pointing the thermometer slightly toward the person’s belly button. If you encounter any resistance during insertion, you must stop immediately and withdraw the thermometer.
Throughout the measurement, stabilize the device by holding it loosely with two fingers while cupping your hand around the person’s bottom to prevent sudden movement. Hold the thermometer steady until the digital device signals the reading is complete, usually indicated by a beep. This typically takes about one minute with a digital thermometer. Once the signal sounds, carefully remove the thermometer and read the temperature displayed on the screen.
When to Use Other Methods
While the rectal method is highly accurate, there are specific circumstances where it should be avoided. Individuals who have recently undergone rectal surgery should not have a rectal temperature taken. Patients experiencing severe diarrhea or who have low white blood cell counts (neutropenia) should also use an alternative method.
Rectal temperature measurement is avoided in people with rectal or anal issues like hemorrhoids, fissures, or a recent rectal bleeding diagnosis. Alternative methods include temporal artery (forehead) scanning, axillary (armpit) measurement, or, for older children, oral temperature taking.
Armpit readings are the least reliable and should be confirmed with a more accurate method, such as a temporal scan, if a fever is suspected. After the reading is complete, carefully remove the thermometer. Clean the device thoroughly with soap and water or an alcohol wipe, then store it safely. The thermometer should be clearly labeled for rectal use only to prevent cross-contamination.