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A navel stone mimicking a urachal sinus
  1. Hidehiko Nakano1,
  2. Takashi Watari1,
  3. Yu Suganami1,
  4. Yasuharu Tokuda2
  1. 1Shonan Kamakura General Hospital, Kamakura City, Kanagawa, Japan
  2. 2General Internal Medicine, Tsukuba University, Mito, Ibaraki, Japan
  1. Correspondence to Professor Yasuharu Tokuda, yasuharu.tokuda{at}

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Anyone can experience finding a navel lint in one's own navel, but how does it become big?

A navel lint, also called navel fluff, belly button lint or belly button fluff, consists of cloth-like fluffy fibres mixed with cutaneous scales, fat or protein.1 Several case reports indicate that a navel lint could cause omphalitis or even sepsis.2 ,3

A 96-year-old woman presented with a 2-week history of recurrent fever and loss of appetite. A diagnosis of urinary tract infection was made based on the presence of pyuria and bacteriuria. However, we incidentally noticed a hard, smooth and well moving palpable mass just under the navel on abdominal examination. There was no redness, tenderness or crusting of the periumbilical skin. While examining the mass, a part of it looked like a navel stone was protruding from the navel.

An abdominal CT scan demonstrated a round, calcified high-density mass behind the navel (figure 1). The radiologist suggested the possibility of the urachal sinus, which is a congenital remains of the urachus. We removed it by soaking in sterilised olive oil. The mass was easily removed from the umbilical cavity (video 1). The pathological finding showed nodular tissue composed of lamellar horny materials with focal microcalcification (figure 2).

Figure 1

Abdominal CT scan show a round-shaped mass behind the navel.

Figure 2

The microscopic image show nodular tissue composed of lamellar horny materials.

Video 1

The removal of the mass from the umbilical cavity.

Learning points

  • Big navel stone could mimic urachal sinus.

  • Navel lint usually does no harm, but its removal may be advised since it could sometimes cause omphalitis or even sepsis.

  • A navel stone can be removed easily by soaking it in sterilised olive oil.


The authors thank Dr Izumi Kitagawa for his valuable support for our work.


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  • Contributors HN, TW and YS cared for the patient. TW and YT wrote and edited the manuscript.

  • Competing interests None.

  • Patient consent Obtained.

  • Provenance and peer review Not commissioned; externally peer reviewed.